My husband and I have a day layover in London before heading back to the states and we want to do a little sightseeing but not stay too far away from LHR. Does anyone have any hostel or B&B suggestions? Or know of any sights that are convenient to see in an afternoon? Thanks in advance for your help!
For easy/quick travel from London to LHR, plan to stay near Paddington Station and take the Heathrow Express or Heathrow Connect to the airport. In April I stayed at "Number63," a hotel 10 min by foot from Paddington. It is on Bayswater Rd across from Hyde Park and Kensington Gardens. A Tube station (Lancaster Gate) is 1/2 block from the hotel. There are many hotels in the Paddington area.
Hostel or B&B? With that budget, take the tube (subway) into London instead of the Heathrow Express or Heathrow Connect. Stay along the Piccadilly Line and you will have no changes. The Earl's Court area has some lower priced hotels and is 45 minutes from Heathrow by tube. The King's Cross area, about 60 minutes from Heathrow, also has some cheap rooms. Russell Square is another possibility. Central London really doesn't do B&B's. Sorry, I am not familiar with hostels. Sights? See anything that appeals. Rick's Westminster Walk gets you past a number of sights and is an excellent introduction to London. Consider visiting Westminster Abbey or Churchill's Cabinet War Rooms or the National Gallery on this walk. Other options are too numerous to mention.
I would suggest Windsor which is a 15 minute taxi ride from Heathrow. You could see Windsor Castle, Eton, Windsor Great Park, Savill Gardens. Alma Lodge is a nice B&B, also there are several nice hotels in Windsor.
Save some cash... take the tube from LHR to Kings Cross, walk 4 or 5 minutes to the Alhambra Hotel. Clean, quiet, family run. Your room price includes a full English breakfast. Tube back to LHR. The British Museum is a 10 minute walk away and free. (I recommend the Museum Taven pub across from the main entrance). All the usual attractions are easily accessed by tube from Kings Cross PM me if you need more info
If what you want is a quick tour around London, get on one of the hop on hop off buses. You will pass by all the big name sights, and then you can choose which ones to hop off and see. With a limited amount of time, this may allow you to see a lot. If you don't want to go into London, then Windsor Castle is a good option, as someone else suggested.
Unless this is your only chance to see a bit of London, I suggest you follow Robin's advice and stay in Windsor. We did that on our last trip (thanks to Robin) and it was great. We took the local bus from T5; it cost about 3 pounds 40 each if I remember correctly. We booked at Frances Lodge, a B&B in Frances Road, 90 pounds for a lovely modern room with huge bathroom and all the "mod cons." Plus a gourmet breakfast. The bus stop, by coincidence, was right across the street from the B&B. We enjoyed a walk throug Windsor and along the river in the evening (could have toured the castle earlier but chose not to), walked into Eton to marvel at the buildings and the 16-year-old buys in tailcoats, then enjoyed a wonderful dinner that cost considerably less than it would have in London. In the morning we watched the changing of the guard, then caught the bus back to Heathrow.
If all you have is one day, I would take either the Heathrow Express or Heathrow Connect trains into Paddington, and stay in the Paddington area. Its quick and easy to get back to the airport for your flight out. As to hotels - there are a ton in the area, just depends on your budget. Bayswater Road is a short distance away from the station, and there are several nice hotel options there. Thistle and Hilton come to mind. There are also a multitude of cheap places to stay in Bayswater.