Hey DA42,
There has been some good information in this thread. Let me give you some more info.
First of all, if you plan on doing your exams in the UK, your initial class 1 medical must be done at Gatwick at the nice price of £341. Now, you can actually get your initial done in another country and have it transferred to the UK CAA for a nice fee. I know a couple guys who did this. Last guy who did this is still waiting for it to be transferred over as he is on a "waiting list.".
Also, unless you get prior approval, you will need to do your flying for your initial CPL issue in the UK as mentioned before with a couple exceptions. Exception 1. Go to Ireland as they have a standing agreement with the UK
Exception 2. Go to FTE Jerez in Spain, as they are actually a UK registered FTO
Exception 3. Go to the USA (with the bargain you could get on the dollar this might be a good option. For example, a Piper Arrow dual in the UK runs around £230-320 = $380-530 US!! In Florida, you may find an arrow for $260). As was said earlier, it is a personal decision and you do what's best for you, many have gone down a different route.
There maybe other exceptions that I'm not aware about. I have been told that Greece accepts UK exam results. There is also an outfit in Spain who claims he can do a license conversion for you with exams from any JAR country but I didn't take him up on his offer so I dont have first hand knowledge.
Now, once you've already done your CPL conversion, you can add ratings. These can be done in any JAR country and then your country of license issue will add them to your license. So for example, if you get your CPL in the UK and then want to add the ME and Instrument Rating in Spain using a Spanish school, you may do this.
As far as CPL conversion hour requirements, there are no minimums. Just whenever you're ready. IR must be done in Europe and 15 hrs is the minimum, 10 hrs can be done in a sim.
Lastly, I used Bristol Groundschool and can't recommend them enough. I also stayed at bed and breakfasts while doing my exams and brushups and it saved a bit of money compared to a hotel.
Good luck. I actually enjoyed the whole process and it was a good experience apart from being away from my family and spending all my money to get it done
Edit: I just noticed the date too haha oh well