Snow,
I'm applying for lots of nothing at the moment but it appears that people are only interested that you do the CPL and ME/IR at the same place. where you do your PPL or your GS is largely irrelevant.
There has been significant reports at OAA that they do tend to forget the modular students in preference to their integrated ones and I did meet several integrated students that had to wait 2 to 3 weeks between 170A and the IRT/CPL test which in my opinion is wholly unacceptable. That said you will come out of the sausage factory and you'll probably be a decent instrument pilot so I doubt it will be a big deal if you do choose that route, just remember to be patient, although honestly at this point I would seriously consider joining their integrated program and see if they will let you skip the ATPLs which you already have, you'll be much more likely to get a job - that being the case I would definitely go for CTC over OAA.
If I was to do it modular all over again I would do everything at Airways Flight Training in Exeter, I've sent 3 friends there and I did my IR there - what an excellent place to train with truly experienced instructors. You will come out a far better stick with a far better attitude than if you stick at OAA or CTC.