Haven't been to UK in quite a while, but I wouldn't think York is really do-able as a day trip from London, as it's +200 miles. Even by train, that's most of the time travelling. On the other hand, Windsor is less than an hour; Bath is about 100 mi. Doing both in one day could be possible, but tiring. I did find this on another site:
http://www.ricksteves.com/graffiti/helpline/index.cfm?topic=12084

Agree that York is too far to do in a day. I would opt for either Windsor or Bath, but I think both in the same day would be pushing it as you would only scratch the surface of what there is to see, especially in Bath. Both can be reached by train from London.

Regards
Vicky
http://postcards-pfte.blogspot.co.uk/
Celebrating the Great British Coastline

I think I'd do Bath, or Windsor castle - I certainly wouldn't try both in a day

York is only a half hour longer by train than Bath, two hours versus 90 minutes. Don't rule it out based on distance! They are very different places, take a look at what each has to offer.

I would want a full day in Bath so would not want to do both Bath and Windsor in one day, but if you get your skates it's of course " doable" by train or car.

Assuming OP is arriving at Heathrow

Bath is easily reached from Heathrow by coach. You could arrive at Heathrow, travel to Bath, stay overnight then take the train to London.

Windsor is 20 minutes from Heathrow by taxi - so it makes a good last night stop.

York is 2h30m from London by train and is easily reachable from central London - just ensure you know how you are going to get to Kings Cross for an early train as the Tube may not be running early in the morning.

So assuming around a week for your stay

Day 1 - arrive Heathrow, travel to Bath
Day 2 - Bath am, travel pm to London
Day 3 - London
Day 4 - Day trip to York
Day 5 - London
Day 6 - London am, Windsor pm
Day 7 - taxi to Heathrow

You could consider going directly from Bath to York by train - take a route that takes you via Bristol in order to avoid London. The travel time is about the same as the total travel time of Bath to London and London to York. That would mean your trip would become a loop with no backtracking.

Sorry to tag on the OP, but I have a similar question. I have researched options from LHR to Bath. I looked at both the coach and Heatrow Express to Paddington Station, and First Great Western train to Bath. I checked the National Express web site and the trip is 4+ hours. By taking the Heathrow Express to Paddington and FGW to Bath Spa the total travel time is apx 2 hours. We arrive LHR on a Sunday,that may be why the National Express options are limited. Am I reading this correctly?

Thanks

Try National Express to Reading, around 45 min direct to Reading rail station, then train to Bath.

National Express has various options for "Heathrow", but it is probably better to use the timings for Terminals 1 & 3, since they offer a non-stop service to Bath. You can travel free of charge between the different Heathrow terminals, which are some distance apart.

The indirect services from Heathrow to Bath all go via Bristol, and include a long wait there for a connection. The direct services usually take under two and a half hours. The single fare is about £20.

Cathinjoetown and chartley,

Great suggestions and thanks. I will check these out. I find I need a solid plan to overcome my "thickheadedness" from jet lag.

I checked the National Express web site and the trip is 4+ hours

I take it you are arriving at T4 or T5. If you use the T1 / T3 option you'll find direct coaches that take half that time. Travel between terminals is easy

http://www.heathrowairport.com/heathrow-airport-guide/travel-between-terminals

Unfortunately I can't tell you the routings for Heathtrow to Bath as the NX website has been goosed all evening

I'm always surprised when I see York dismissed as 'too far' for a day - and then somewhere else just as far is suggested as an alternative.
Kings Cross to York is actually less than 2 hours if you pick a fast service. We live near York and my husband commutes easily to central London every so often for business meetings - as do numerous other people.
Once you are off the train at York you can be into the city centre within minutes and by foot - it is compact and very walkable. There's so much to see and do, although some people think the Minster alone is worth the trip. And yes, it is an extremely beautiful city.

alanRow,

You are correct. Arrival from the US at T5. I checked the options outlined above and checked the Heathrow web. I get bus 441 from T5 to the CBS and in 2H 45M and L20 later I am in Bath. A good economical easily executed (with a jetlagged brain) solution.

As alway The Fodor Nation has the answer