The cost of doing a survey very much depends on the time it takes to complete. What kind of survey is being completed? How big is your site? How many rooms are within that site?
I don't think £1500 is a lot of money for a proper survey to be completed, as it can take a good day to do the actual wandering about on a reasonable sized site, and then a day to complete the report. At professional rates, £750 a day isn't a huge amount realistically (you have to take account of travel costs, potentially hotel costs, the staff costs, equipment costs, insurance, overheads etc...).