There are three schools at Cranfield at the moment: Billins, Bonus and Cranfield Flying School.
Billins is a friendly and relatively inexpensive, but small, flying club/school with a handful of aeroplanes.
Bonus is a large and well regarded commercial school, who can take you all the way to fATPL, and have a lot more aeroplanes, they are a little more expensive.
CFS has changed its name a few times over the years, and is basically Coulson Aviation of old. It seems to sit somewhere between the two in the way it's run. Personally I always found David Coulson rather hard work, but equally he is little seen on campus these days and they seem to be operating reasonable aeroplanes with sensible instructors.
I've flown with all three, and each have strengths and weaknesses. On net however, I think I'd recommend Billins for NPPL/PPL/IMC, and Bonus for anything beyond that. I'm not sure that I see real benefits at CFS over the other two players.
There is also a Thompson flying club there, about which I know little I'm afraid so I can't really comment - good or bad.
G