I flew at Cardiff too and found them a decent bunch, hope things go well there.
Haven't been there for a while but t my knowledge they do not do professional ratings, only PPL/twin/IMC etc.. So for 0-ATPL you will have to go elsewhere anyway.
Aero's are based at Glos and Filton and are excellent, I did my CPL with them and actually left CWFC to become a member at Aeros, great fleet great instructors.
Bristol Flying Centre at BRI have an excellent reputation also, but I never trained there and so can't really comment.
I did however go to Bristol Groundschool, which really is a superb place, I would highly recommend them for your writtens.
Regards and good luck.
Paul