CAT3C,
I, like you have had to try and draw some sort of conclusions from my training providers.
To stick to my professional training: ATPL's: went to the best available at the time PPSC.
CPL: Looked at them all but decided after spending an absolute fortune on the accomodation away from home while in groundschool, to go for somewhere within easy reach that still had a professional feel.
Decided on Stapleford Flight Centre. Reasonably close to home for me, very well priced compared to most, professional, friendly, very good facilities and aircraft, so hence the first time pass!
IR: Not started it yet, but will be going back to Stapleford to do it there!
I think IMHO that it really depends on your personal circumstances and for lengthy training like the ATPL's, CPL and IR, accomodation costs can really rocket up, so a good school somewhere close to home would be the best bet, to try and avoid the extra living costs.
Like you said, all the schools offering the courses are approved, but there are some that I wouldnt touch with a barge pole.
This country is obsessed with a false class system, so if you were to view these schools in the same way you'd have the perceived list something like:
1. upper
2. middle
3. working
being...
1. Oats, BAe, Cabair etc etc
2. Stapleford, PAT, Bristol etc etc
3. Joe bloggs..
I personally think this is not quite true and i'm therefore only using it to make a point, that if you're loaded, want a pedegree Integrated course (which may look better on the CV) then go to 1., if you're not a tycoon but still want top quality modular training, then go for 2., if you really like to cut corners and dont want to fly professionally, go for 3.
I'll finish with a genuine line from a letter received only a week ago from a large uk airline:
'We do not have any preference for any particular flight training organistion'.
Good luck in your quest!