I've just had two quotes for ones close-ish ot me actually.

Dennis Vessey @ Brigg charges £30 for a power run. Not sure if this is like Christian said tho: just 1 run or a couple to get an average, or inc VAT.

Corten Miller @ Boston charge £47 inc VAT for the power run plus graphs.
£70.5 per hour for setting up. They have a new fandango rolling road as well.
http://www.corten-miller.co.uk/