737-fanatic, Im in a similar position at the moment. I am just doing my ATPLs through Bristol, and looking at where to do my CPL and IR after I finish. Due to work commitments (as in I need to work to fund my training) Im left with a rather limited choice of schools. I wont name the schools directly, but one is well known and does both CPL and IR and the other is lesser known but comes highly recommended, it however only offers CPL so I would have to go to the other school to complete my IR. I personally dont think this should be a problem as the CPL only school does seem to be more flexible to meet my needs and I was impressed with what I saw when I looked around (let alone the positive reviews Ive heard about them).
Anyway, Ive done a little bit of digging and have received a mixed response. However two responses which stand out for me are the response from Eastern Air and Flybe.
Eastern stated "It is preferable to complete your CPL and IR at one school as this provides an audit trail for the airline and displays continuity."And Flybe pointed to the website which states "Modular candidates should have completed training at a single FTO, not including basic PPL training or ATPL theory study and examination" I still have not made up my mind, but I would suggest you try and talk to the airlines (or whoever you hope to work for) and see what they say. My thought is that if you can explain it in an interview then it should be ok, but my worry is that I might not get to interview because of the different schools listed on my CV.