Deano is right the TraxFax works well and Aeros really are superb (I did my CPL ME/IR with them just over a year ago). Gloucester ATC works well and delays aren't normally a problem. Exceptions may be on a CAVOK weekend with free landing vouchers (but commercial training at Aeros is usually Mon-Fri) or Cheltenham Gold Cup week (but they work around it).
Doing the IR bit out of Bristol was good in that it gave a 'commercial airport environment' but delays for Easy A319s, Ryaniar B737s etc were not a problem. BFC at Bristol also looked a very good outfit and certainly gets good recommendations. I believe they do the ME/IR first then the CPL (either SE or ME).
Whilst on the subject of minimising delays at a commercial airport, have you looked at Airways Flight Training at Exeter. They have an excellent reputation and Exeter doesn't seem to suffer from holding delays. In fact if you do your IR training out of Bristol (or Gloucester or even Bournemouth?) you are likely to make a lot of approaches into Exeter.
Anyway good luck 'VFR Transit' wherever you do your flying training and don't forget to enjoy it as it will be over before you realise it!
FB