Try this for size:
You have a FAA CPL/IR. Get a JAA PPL, you only need a Skill test + RT Licence, with JAA exams you are exempt the 2 PPL written exams. Add your ME rating to the JAA licence, Skill Test + Ground Exam.
Now do a JAA IR, you will get credit for the FAA IR and in theory could do it in 15 hours, but allow for 25. A PPL with an IR is more use than a CPL without one.
With the IR you will get a 10 hour credit towards the CPL leaving only 15 hours to do.
Then do a FI Course in the UK.
Remember once all the exams are passed you only have 36 months to get CPL and IR issued.