Had similar on my old citroen berlingo....cooling fans were on constant which i obviously told them beforehand, and they would need the van for a whole day to complete the work (which lets be honest couldn't be too hard to rectify lol). End of day same as you picked the van up to be given a £100 bill for diagnosing what was wrong and would have to book the van in again for the work lol
I can't stand main dealers and the ridiculous charges/procedures they seem to follow.
Seems it's standard to charge an obligitory £100 odd just to diagnose what's required regardless of what you tell them so don't know quite how well you will get on....good luck!!