From a basic "foreign"ICAO CPL to a JAR ATPL is a long and expensive process.
Medical at Gatwick. You should get away with 189 pounds for that.
You are looking at having to do the 14 ATPL exams again after doing either 6 months groudschool or XX months Distance Learning.
There is discussion about concessions for ICAO IR's. As it stands at the moment you'll get maybe 5 hours off if you have some multi time. So, another 50 hours for a multi IR (JAR).
Then add in a MCC course...
It all adds up...
As far as I know, no one is doing JAR CPL theory hence the need for the ATPL theory.