If you are close to your 1500hrs mark you are better off to wait and get your ATPL in Canada,because then the things change radically. You only have to do two exams instead of 14 and your licence becomes automaticaly JAA ATPL.
Not quite. To take this option you will need at least 3000 hours total experience
on aircraft over 30,000kg MTWA of which at least 1500 hours must be as PIC (Captain). Then, as you say, you are credited with the theoretical knowledge exams except those in Air Law and Human Performance & Limitations.
However, this UK-only arrangement is not fully in accordance with JAR-FCL and the licence will be endorsed
"Valid for United Kingdom registered aircraft". If you wish to fly an aircraft registered in another JAA member state, you will have to gain the permission of the NAA of that state and not all will grant it.