Chris
I must say it seems like ages since I flew from cranfield (in reality its only been about 6 months) but I can certainly recommend Billins Air Services. I did my PPL, night rating and IMC with them, never had any problems.
As has been said the only main drawback with cranfield is having to hold at times, either waiting to depart or waiting to rejoin. although i'm now flying from east midlands which is far worse due to commercial traffic. but cranfield ATC do their best to handle lots of aircraft and keep everyone happy.
I'm heading back to cranfield over easter (getting kicked out of uni for 4 weeks) so I might see you there. Good Luck with the PPL.
Cheers,
Owen