Where to stay night before flight from Heathrow

A few years ago we drove down from York to Derby area. Toured Chatsworth House (you could also do their gardens, or their farm) . Leaving Chatsworth in late afternoon we got as far as Bedford, pleasant little town, nice hotels for the night. next morning was a fairly easy drive to London. (Not much excitement to se in Bedford, but we found a short walk to be quite interesting Or you can skip Chatsworth drive directly to Bedford and tour Woburn Abbey or the Shuttleworth collection

We're headed to England about a week after you and have an oubound flight from LHR around the same time. Although we're staying more than one night, consider setting up around Kent (we're staying in Maidstone). Centrally located for Canterbury, Dover, Leeds Castle, etc. I'm sure someone else will recommend Windsor....plenty of options.

We turned our car in the night before, making sure there were no problems ( traffic jams, wrecks, etc.) on the leaving day. We stayed at the Ibis Hotel on Bath Road. We walked from the Ibis towards Heathrow about two/four blocks, turn right towards Harlington, and go to the White Heart Pub, which on the left. It is about a 12-15 minute walk. http://www.inapub.co.uk/pubs/white-hart/harlington/UB35DP/22856.aspx. We had a great meal and wonderful conversations with several British Citizens. The next day, we caught the free red bus back to Heathrow and flew home. I am not sure about the bus numbers. Something like 400 or 500? Maybe someone else can chime in on this or I can go looking if you need me to. There is also a pay bus, about 10 pounds each. I opted for the free one.

Windsor is really nice and you can walk along the river (thames). check out B&B called Frances Lodge. I'll bet they have parking and everything. Prices are good and so is breakfast.

Thanks to everyone who responded. I like having options and we'll see how ambitious we feel at the end of the trip. I was getting so hung up on this one day out of 30!

We had a lot of success sightseeing all the way up until the last minute the night before our flight, and sleeping in Slough which is not far outside London and 10-15 minutes drive from Heathrow. There is a Holiday Inn Express that is inexpensive and pretty nice. Parking is free. Then you can get up in the morning, grab your rental car and go. I also highly recommend not dropping your car off the night before - by the time you pay for the Heathrow Express and switch trains, you might as well have kept your car.

Dropping your car off at Heathrow and going to the airport via shuttle is free. Then get the free bus that travels down Bath Road to the hotels. Go to the pub I suggested above, for some relaxing conversations and good grub. Walk back to the hotel, sleep well, get up and catch the red bus back to Heathrow to fly out. Bus no. is maybe 55, or 500? NO hassles the next morning, no flat tires, no wreck and you are hung up in traffic and cannot get there, no hurry and turn in the car and later be billed for damages you did not do because you did not have time to have them inspect the car and sign off on it, etc.

I would drop the car off at Heathrow then take taxi to Windsor.
There is enough to see while in Windsor, you could tour the castle, walk to Eton (a five minute walk)....this is where Eton College is which is actually a middle/high school, where most of the royals send their boys along with other wealthy families, could take a taxi to Savill Gardens..which are beautiful. Have a great meal in one of the pubs. Have a great trip.