If you just want to do a CPL and don't think you will ever do an IR then you can do the CPL distance learning course for the 9 exams. Distance courses are available from GTS at Bournemouth (who I'm hoping to go with, assuming I pass the medical on Tuesday!), Atlantic Flight Training at Coventry and Cranfield College at, errr Cranfield. Prices are around the £1,500 mark to which you have to add £55 per exam.
If you think you might do an IR in the next few years then you need really to do the full ATPL course and exams, of which there are 14 (do the CPL and IR exams separately and you end up doing 16 exams and it costs alot more to do the two separate courses for CPL and IR). The courses are normally broken down into two or three sections with a week of revision lessons at the College at the end of each. The revision sessions are timed to be held just before the exams.
To start a CPL flight course you need 150 hours total time. To apply for the issue of a CPL after a successful skills test you need 200 hours total of which 100 hours must be P1(PIC), at least 20 hours must be cross-country as P1 including one flight of 300 nm which includes landing at two other aerodromes. You must also have a Night Qualification.
Since the CPL is 25 hours you really should have about 175 hours/100 hours PIC before you start the course or be prepared to build up the required hours before the skills test.