Jack
Hate to be negative. There was a fast track procedure, but that involved you having in excess of 1500 hrs PIC on a plane greater than 30k kilos, from memory. If you then did the Air Law and Human performance exam and passed an observed skill test, you got your UK ATPL. Anything less than that almost invariably involved doing the whole lot!
The arbitary 30k weight rule in my opinion is ridiculous. why would an experienced Capt with 1501 hrs on a B737 be more acceptable than a guy with 10k hours PIC on a Dash-8 for example? But rules is rules.
Ask the CAA, but don't hold your breath. Good luck