Hi there.
If you use the search function you will find quite a few threads relating to this topic. However here are the basics.
In order to convert your non-UK CPL/IR with ATPL exam credits to a JAR one issued by the CAA you need to do the following:
Sit the ATPL exams. Despite what some ground school places may tell you there is no need to sit the full course - it is at the training providers discretion. However in order to pass the JAA ATPL's you will probably need to do a fair bit of study anyway.
Pass the JAR CPL skill test. There are no minimum training requirements, once again it is at the training providers discretion. Sit the test in a multi-engined aircraft and you are also granted an MEP class rating.
Do the approved IR course. There is no dispensation for holding a foreign IR. In your case it would be a 50 hour course.
Pass the JAR class 1 medical. Slightly going off subject but can anyone tell me why you must pass the medical in the state where you do your training. I thought that was the whole point of JAR, to eradicate differences in licensing standards across Europe.
Basically you're looking at at least £15,000 to convert your licence.
Hope that helps.