Help Needed With UK Itinerary

For this trip I think basing yourselves in Edinburgh might be a good idea. You could do a "coach trip" through the Highlands one day to get a taste of that part of Scotland. If you'd rather, though, you could go up to Inverness and base yourselves there and save Edinburgh for another trip. Either would work. Early July is a lovely time for Scotland. If you've "done" London you could also cut your time there and add more time in Scotland.

Kristina, I don't have much to add on your primary question. However, on a trip a couple of years ago, we wanted to to from London to Cheltenham and York. I generally opt for train travel. Found trains in GB to be very expensive. Found that renting from Enterprise car rental was far more economical. Also convenient for seeing sights away from major transportation points. We rented at Heathrow and returned there. Don't know about drop price if you return to Edinburgh but it's worth a search.

There is no train direct to Avebury, Avebury itself is very isolated. By public transport get the train to Swindon, then a bus to Avebury.
If you are going to York after, you probably won't have the time to make York that evening, why not overnight in Oxford ?

Hi. My wife and I just returned on Monday from our two-week tour of Bath-York-Edinburgh-London, and like you, we'd both done London before and traveled exclusively by public transport. Here are a couple thoughts I have, while it's all still fresh in my mind.

1. York is wonderful, very compact, and the signs get you from place to place easily. We saw most of it in a day and a half, but personally I'd recommend two full days. Delightful place.
2. Check the rail listings now and see if you can make your connections, especially Avebury-London-York. This may change by next summer, but in October there was major work on the rail lines. Our anticipated 2.5 hour trip from York to Edinburgh took 4+ hours.
   
3. Edinburgh's major sites may all be along the Royal Mile, but it's the longest mile I've ever experienced. Unlike York, it was much more difficult to get from place to place quickly. (Princes Street is under major construction, so the quick routes to many places are very congested.) If you have any "must sees" in that great city, be sure to give yourselves enough time.

Sadly, we had to cut Hadrian's Wall due to time constraints. There are bus tours from Edinburgh to key sites along the Wall. You may want to consider that option instead of hiking with your full bags.

Enjoy!

Thank you for your replies/suggestions/advice. After reading what you all had to say, we've revised our UK itinerary to the following:

We will spend 2.5 days in London however one of those will be a tour maybe to either Windsor Castle/Stonehenge/Oxford or Salisbury/Stonehenge/Bath. That way we still have time to see/do the few things we missed the last time in London and get to visit some new places.

We will go directly to York from London spend a day and half and then go directly to Edinburgh from York.

We are making Edinburgh our homebase for the last 3.5 days and taking a tour up into the Scottish highlands one day and another tour into the Scottish lowlands (including Hadrian's Wall) on another day. That still leaves almost 2 full days to explore what we want to see in Edinburgh.

Thanks again for your replies and any advice on a day tour out of London would be appreciated!