Thats very expensive for a rolling road session. Typically I would expect them to be £30-50 for a half hour session - do a couple of "runs" and take the average.
You could think about group buying, where you could book a session for a couple of hours and invite friends along who also want a dyno run - this lowers the cost significantly.
The best option by far though would be to sign up to an arranged meet - or even organise one yourself! Keep an eye out on Meetings in the forum for future events. Prices can then range from £15-40.
Good luck!
