If you get a job on type, I think you can do it for a year without converting providing you have an ATPL. This gives you the chance to do the exams and the flight test on your current type.
If you dont have an ATPL then you have to go through the whole thing except your physical training reduces to "discretionary" training for the CPL and 15 hours for the ME/IR.
I think you would need the full ICAO ATPL though. Do a google search for LASORS, the general rules for the UK CAA. I think you want section D. Alternatively email the CAA and ask them, give them all your details. They will probably point you towards LASORS.
You also have to get working rights and if you are Aus or NZ then this (last time I heard) has now reduced to 1 year work + 1 year travel.