UK & Ireland 16 days

No- 16 days is not enough time to see it all! That said, you CAN see a sample of each part of the UK (though you did not mention Wales). I hope you are not planning on taking the car you rent in Ireland to Scotland- you'll pay a hefty drop fee if they even agree to let you do that. You can rent another car or use the trains. Is London the only part of England that you are interested in? Personally with 16 days (really 14 by the time you discount getting there and getting home), I'd limit myself to England and Scotland. While you have LOTS AND LOTS of options, here's what I'd do: Fly into London-3-7 days with possible day trip (pick or maybe 2 of following: Windsor, Cardiff Wales, Canterburry, Dover, Winchester, Brighton, Stratford-upon-Avon, Bath, etc.) train to York- 1 or 2 nights train to Edinburgh 2 or 3 nights train to Aviemore- 2-4 nights (lots of activities here, distillieries, microbrewery, stream train ride thorugh countryside, funicular or hike up Mt. Caringorm, other hikes, cannoeing, horseback riding, etc.) train to Inverness- 5-7 days (possible day trips/activities include Cullodean Battlefield and Clava Cairns, Eliean Donan Castle and Isle of Skye with lovely glens thrown in, cruise on firth for whales and dolphin sightings and black Isle, cruise up river Ness to Lock Ness w/ Urquart Castle and Drumnadrochit village stops, more distilleries, shopping, etc.) train to Glasgow- 1-3 nights- fly home As you can see, you've only hit some of the highlights and have MORE than you 14 days filled. And we haven't even touched Ireland or Wales.
Plan on going back!!! Alternative is to hit 1 major city in each country- London, Dublin, Cardiff, Edinburgh- spend 3 days in each- but you loose alot of time getting from city to city that way (or you loose alot of money on flights).

Thanks for the thorough reply Toni; I totally appreciate you taking the time to respond to my post. Bummer about the car rent. So, it appears that the best thing to do it ditch the car idea and get a Britrail pass. Then travel by night as much as possible and at least if plans change we can just hop on the train to the next destination. Does the Britrail require reservations or can people book at the time they wish to travel (day of)?

Hello Arica, I agree that 14 days is not enough time to really see all you have listed. Bear in mind that although distances are typically shorter between cities in the UK than they are in the US it still requires time to travel between cities - in general figure about 1/2 of a day to get between one place and another by the time you figure in transport to train station, trip and transport to new lodging. Also, given the short amount of time you will have, a Britrail pass may not be the best option financially - it would be much cheaper to simply buy individual tickets. Since you are planning to travel in September, you have time to plan out your trip and buy your tickets in advance which is generally cheaper. My advice would be to develop an intinerary based upon what you want to see and then plan out your transportation from there.

If the Ireland ferry port and the Stranraer ferry port have car rental desks, then it isn't that difficult to return the Irish rental car, take a ferry, then pick up the Scottish rental car. However, your trip might flow better if you start with a bit of London, take a train to Edinburgh (consider an overnight in York), get your rental car for Scotland (Glencoe is great for hiking), turn in the car, ferry to Ireland, get second rental car, fly home from Shannon. With limited time, I would skip Dublin......You could also do this itinerary in reverse.

I'm pretty sure the Stranraer ferry port is out of business and the operation has moved up to Carinryan.

Thank you everyone for the advice.... truly appreciate it. It's very difficult to plan an itinerary for places I've never been-I am overwhelmed but SO GREATEFUL for this site and people like you all that take the time to respond. I think it is starting to almost, kind of, come together. ;) Have any of you stayed at or know anything about St. Christopher's Inns - Hostels? Specifically "The Village Hostel, 161-165 Borough High Street" in London it is inexpensive but very mixed reviews on tripadvisor. Thanks all.

As Californians skip dolphins &I whales see them in Carmel. We did a rail-drive trip with 8 days of train & seven with car, not indluding 3 in Ireland. Skip Glasglow. Visit Scotland in late Aug. for Tattoo & Fringe festival. Skye in a favorite. Glencoe is a very peaceful and spritual land, a r.eflection on a sad time. Go. Our route was fly to SFO-Gatwick. 2 nites London w/plSays. Drive to Dover, sing song. Visit Brighton Visit winery in Isle of Wight laffable, Drive like the wind to Wales 1 nite see castle, turn in car. Ferry to Ireland. Spend in Waterford, have it mailed home. Kiss Blarney stone. Automatic car breaks down in Limerick. None available. I drive old stickshift to Dublin 2 nites. Ferry to N. Wales, train to Glasglow (skip), drive to Skye, drive to Invernes, keep watch on Loch Ness. Visit music museum, play with instruments, then Edinbrough. Stay at Thistle Inn. Walk Mile, I see shops, he visits Scot Parliment, visit castle. Train London. Little side trip to pottery district for 2nd hand Wedgwood. I shop London, he visits Oxford. This was the '91 trip. We have been back 4 times to Scotland. Consider joining Servas.org and staying 2 nites with real people. In '91 Scots were talking about home rule. It now looks more likely. Just enjoy,
Betz