I did the conversion recently. You have to do the following considering that you have a non JAA CPL +IR +ME:
Successfully obtain a JAA Class 1 medical
Complete an ATPL theory course, either by residence or distance learning (takes about six months full time study if you do distance learning)
Complete the 14 ATPL theory exams
Complete a CPL flight test (no minimum hours required but expect around 10hours). If you complete this in a single engine aircraft, you will have single engine privileges, and if you do it in a ME, you will have ME privileges, but not SE.
Complete a minimum of 15 hours of Instrument training in JAA land, up to 10 hours can be counted in a FNPTII (simulator).
Complete an IR flight test. If you do this in a multi-engine aircraft (which is what most people do), you will have an IR valid for multiengine and single engine aircraft
Pass a test for the issue of a radiotelephony license.
Not required, but if you want to work at an airline you will need to do the MCC course
If you want your license from the UK, you will have to take the CPL skills test with a UK examiner. The medical can be done in other JAA countries but the papers have to be transferred to the UK and be issued by the UK CAA. The theory exams should be taken in the UK. You can then add ratings in other countries, such as the IR rating.
Use the search function... this has been well discussed. But to give you a head start:
http://www.pprune.org/professional-p...5-figures.html
http://www.pprune.org/nordic-forum/4...ggestions.html