Let's do the positive stuff first: the location is good for Heathrow and the room was very shabby but clean. But...and it's a big but. This place is run by the most unhelpful, rude and unpleasant woman. It's a sort of humourless West London version of Fawlty Towers - not in the least entertaining, just grim. If you like to arrive before 8pm on a Friday night to a deserted guest house, all locked up, and be instructed by text message where to go, then told off IN CAPITAL LETTERS in another text message for daring to ask questions, before, finally, having the phone put down on you by the woman herself...well, if that's your idea of fun then come on in, the Oakwood Guest House is perfect. If on the other hand you would like just a modicum of civility from your host, well, you might wish to book elsewhere. It is of course possible that I happened to encounter this lady on a bad night. Perhaps she had had a particularly trying day. On the other hand - and bearing in mind I am NOT the only person on TripAdvisor to remark on her unpleasantness - maybe this is something fairly common here. Either way some sort of training in how to not be an absolute battleaxe might be due.
If you want cheap, clean, and convenient to Heathrow this is fine. But don't expect to be made welcome and don't expect any help from the management.