Car rental

You can lease a car for up to 6 months through programs operated out of France, and pay pick up and drop off fees for other countries; or you can simply buy a used car and try to sell it later; see links for both options at http://www.ricksteves.com/travel-tips/transportation/car-leasing.

Unless you have long-stay visa, which is hard to get, a tourist with a USA passport cannot spend more than 90 days out of any 180-day period in the countries of the Schengen Visa Agreement. You would have to distribute some of your time to non-Schengen countries, such as Britain and Ireland (where you could drive your car) or Bulgaria, Turkey or Morocco (but may be easier to fly to some of those). See http://travel.state.gov/content/passports/english/go/schengen-fact-sheet.html, as well as plenty of related discussion in this Travel Forum.

I think a lease might work better for what you are talking about. It's at least worth pricing. I leased a car out of Amsterdam then returned it in Rome.

I've found a lease works better for nicer or larger cars and rentals are usually the better choice for the low end economy cars - so when it's just two of us, I find myself renting a standard transmission, diesel, economy car.

The lease was a seven-passenger car for five of us. It worked well. The car was the right size for two adults and three kids with a carry-on each. If we were bigger or had more luggage, we would have been cramped.

The worst part was the agent showing up an hour late in Rome - good thing we weren't catching a plane right then. Picking up in A'dam was fine; the guy there had black painted fingernails, purple hair, and skin tight spandex with holes cut in them - but was on time, efficient and friendly enough. I'll take him over the agent in Rome who forgets to show up.

Good pointer there about the 90 days in 180 limit in the Schengen area; if you decide to take the care from Europe to the UK you will have to notify the rental folk who may prohibit it or charge significant fees; if you take a European car to the UK your wheel and driving position will be on the wrong side making passing difficult, getting barriers up, and going around bends. Because many British roads are single carriageways and they are used by lots of HGVs (Heavy Goods Vehicles - large tractor trailers) and passing will be so difficult you may find your traveling speed curtailed.

I think it will make more sense to rent/lease for the three months are in the Schengen zone and then cross over to the British side and lease again for three months. That would simplify potential insurance issues and solve the problem of the right hand drive cars. Probably cheaper in the long run since you would have to ferry the car both ways if you kept it for six months.

Buying a used car is impossible unless you have an home address, residency which you would not have with a tourist visa.

Thank you everyone for your generous supply of useful info. It would just be myself or perhaps one other person, so a small economy car does seem best (and I'll fit in with the locals a lot better.) Also makes sense to rent 2 different ones; one in the UK - the other on the continent. Sounds like what I dream about doing is totally doable and affordable and would provide the freedom to go where I want, stop when I want and travel at my own independent pace. It could also allow me to camp along the way in the beautiful countryside.

One car for the Continent and another for UK makes sense, also gives you more options for crossing the Channel.

On the Continent, you can rent in one country and drive pretty much anywhere, but if you return the car in a different country you'll have a hefty drop-off fee. It may be worth it to save the time of driving back to Amsterdam (or wherever you rented), so you could fly to UK from wherever you end up on the Continent. But, with 90 days there, you don't need to be as time-efficient as most travelers (lucky you!).

So, I'm wondering... if I return the car to say Amsterdam, where I rented it on the continent, is it more cost effective to fly to the UK or take a ferry (w/o a car - passenger only) Or would it be wiser to rent the car in Paris, tour the continent, return it to Paris and then take the chunnel to London and tour the UK?

Claudia,
There are 3 options Amsterdam to London:
1) Cut price airline. This is the route EasyJet started out on, lots of competition.
2) Ferry Hook of Holland to Harwich, with connecting train both ends. Slow, not recommended, except possibly for the experience of crossing the sea.
3) High Speed Train, changing at Brussels.

You could rent the car initially in Paris, and return it to the same place (As stated above, NEVER rent in one country and return in another, that is very expensive). If you want to include Paris in your trip that is an option, a car in Paris is a liability, as it is in most big cities (Amsterdam, London, ...). Personally I would rent at Schipol, and not drive into any big cities. But you don't have to go to Paris to catch a train to London, Brussels or Lille also have High Speed trains to London.
The train companies (Eurostar) keep promising direct trains from Amsterdam to London, but no start dates have been given.

I think you have reached the point you need to start firming up on what places you will visit in what order, which will decide the methods of transport.
And of course, don't forget the Schengen Area limit of 90 days for non-EU/Schengen citizens.

Lille is a wonderful suggestion. I'm presuming one could take a train from Paris to Lille. It might be good to fly into Paris, rent a car and tour the continent, then return it to Paris and head toward. Or could I rent a car in Lille?

Ideally, I'd like to visit Amsterdam (tulip season), head a bit north to the area of Emden where Dutch German emigrant ancestors came from. Head back south again through the Netherlands, Belgium, into France (i.e; Lyon) down into Italy and around back up through France again, hugging the coastline back toward Lille or Brussels and then cross over to the UK. I do not plan to visit the Schengen countries on this trip.

Trains from Paris to Lille are one TGV (High Speed Train) per hour, journey time one hour.
You could fly into Paris, have some days in Paris, take a train to Lille, one night in Lille (probably enough), then hire a car for some touring of Belgium and the Netherlands, return the car and move on.
With 6 months you have lots of time (but only 90 days in Schengen-area).
See the Eurostar website for trains Paris/Brussels/Lille to London.

Oh Claudia, you just posted "Ideally, I'd like to visit Amsterdam (tulip season), head a bit north to the area of Emden where Dutch German emigrant ancestors came from. Head back south again through the Netherlands, Belgium, into France (i.e; Lyon) down into Italy and around back up through France again, hugging the coastline back toward Lille or Brussels and then cross over to the UK. I do not plan to visit the Schengen countries on this trip."
Emden is in Germany, "Netherlands, Belgium, into France ... into Italy .... I do not plan to visit the Schengen countries on this trip". Germany, Netherlands, Belgium. France, Italy ARE ALL SCHENGEN COUNTRIES. The 90-day clock will be running all the time from when you land (Paris or Amsterdam) until you cross the Channel into non-Schengen Britain!!! It will start running again as soon as you cross the Channel back again.

sorry, I meant non-schengen countries

I hope to spend about 90 days on the continent and the other 90 in the UK. Sounds like it is totally doable. I really appreciate all of the various details about trains, etc. It has been most helpful!

I would rent a car only for driving in the countryside. Car is a big burden in the cities. Britain drives on the left hand side so you want your steering wheel on the right side. You can see much better from there especially when passing slower vehicles. I would not want to drive a car from continental Europe there.

No I agree about having a different car for the UK. I've driven a lot in England and Scotland and am very familiar with that. While I am in a big city I'll park the car and use buses/trains/the tube etc to get around. It worked great in Glasgow, Edinburgh, & London before.
I just wasn't sure if I could rent 1 car on the continent and go from country to country like I can in the UK. Everyone has been extremely helpful, providing websites that I've followed to train schedules, car rentals and lots to think about. I'll definitely be going with a diesel, standard transmission economy vehicle that will suit my needs perfectly. Thank you.

They add a big fee if you rent a car in one country and return it in a different one.

yes, that was mentioned earlier in the conversation Illje. Thank you.