Well we used to have folks stay at this place:

http://www.houseweb.co.uk/ht/bridge.html

However, with ROE, 25 quid is approching $50.

You can take the tube to Hounslow and then a 235 or 237 bus to Isleworth.

That said, have you tried looking at your priceline bidding strategy? Did you check out betterbidding.com? I see some bids have been won in theh $43 price range at LHR hotels. Don't forget there are ways around the losing bids on priceline