Well, trying the Renaissance was a BIG mistake. Arrived at 11:30 to a full parking lot. Their somewhat unhelpful suggestion was to park on the street and move the car back into their parking lot at 02:30!
Below is the message that I sent to them about this:
"I wanted to let you know how disappointed I was with the Renaissance at Heathrow on 11/29/02.
I arrived at the hotel at 10:00 at night only to find that there were no parking spaces. The security guard said that I could park illegally, blocking other people in, and perhaps it would be O.K.
The front desk were equally unhelpful, so I instead went to the Marriott across the street. Perhaps I should have gone to the Sheraton in order to 'punish' the Marriott brand, but I did not think of that at the time. Of course the Marriott was 30UKP for expensive than the rate I had been quoted at Renaissance.
I think that it is unacceptable for a hotel to 'run out' of parking for guests and not offer other options (i.e. valet). The fact that this was at a suburban hotel rather than a city center location makes it even worse.
Worse than the lack of parking was the 'you're out of luck, pal' attitude of the staff."
The goods news is the the Heathrow Marriott was very acceptable, and the staff there, especially in the restaurant at breakfast were excellent.
The Renaissance's response was "we'll try harder next time." No coupon, no freebie, nada.
This might be one to avoid if you have your own vehicle.