I did my Groundschool at CATS, CPL/IR at PAT and a Type Rating at GECAT. I'm now with Monarch. I was asked where I did things and why I chose those institutions, so its worth having good reasons. However, I think Flybe is relatively particular about continuity of training but its not a view universally shared.
So I would always visit the places you have on your shortlist, talk to people who've been there and choose them on how you feel you'd do there. (unless you only want to work for Flybe in which case you should probably go with Cabair)