I believe there's a list on the CAA website, but there's loads of places here in Bournemouth,
I'm doing my ATPL theory currently with BCFT, but there's also Cabair, PAT and CTC.
The difference between Modular Course and doing it all on an ad-hoc basis seems to be the ATPL theory. If you just do CPL + IR, it is not the same as doing ATPL exams then CPL practical and IR practical.
Its hard to see the differences between the modern modular courses and integrated courses. They both seem to take about the same amount of time if done intensively, but the integrated is twice the price and you come out with 50 less hours.