West Hill is £70, Worplesdon £80. We could also do Hindhead at £70 or West Sussex at the same price, but the latter is 1.5 hours driving from Heathrow (although only 45 minutes from there to BUDA headquarters).
Has Fowler's West Surrey been mentioned? It seems to be the bargain of the lot at £60.
Walton Heath is something of a compromise driving-wise, being about 45 minutes from Heathrow as well as BUDA HQ. However, you're taking in a good part of the London ring, so there may be traffic problems.
Ulrich