Over and out,
I strongly suggest that you read LASORS. I am not sure about the CPL route as I held a full Aus ATPL and did that conversion. I had to do elements of the CPL test in my Shorts 330 LST (for the IR) whereas my husband who was doing the same conversion only did a 737 LST in the sim, no CPL elements. I don't think there's much flying involved with the CPL conversion. Others may have factual info on that.
douguie,
You'll need a visa or an EU passport. Unless you have some skills that are highly desirable, such as TRE etc, then it's unlikely a company will sponsor your residency. You can always ask.
9Ws,
If you have +3000 hours with +1500 hours in command on +30 tonne aircraft in primarily international or equivalent operations then you can apply for a JAA UK CAA ATPL. You only need to do 2 exams and the LST in sim (on the aircraft you have 500 hours on). Note, this will only let you fly G-reg aircraft, if you want to fly other reg, you'll need to do the other 12 subjects.
Again, this info is in LASORS which can be found on the CAA SRG website. Please cross reference every thing you see here with that info. It's not easy but it's essential.