hibypassratio
Im in the same boat so this is the info i have and advice i can give.
Turkish has said most of what you have to do.
YOu will be exempt from doing an MCC course if you have more than 500hrs of multi-crew time otherwise save up an extra £2000 or so.
YOu will only get exempt from the ATPL if you have more than 3000hrs on aircraft over 30tonnes. King Air falls a bit short of that im afraid.
You also have to do an IFR conversion with a minimum of 15hrs of flight, thats the expensive part but as turkish said you can try and do it in florida. The rest involves 14exams and i have been told to save up about £3000-6000 for the theory and another £10000 for the IFR.
I know it hurts. Bristol flights school has been recommended alot of people but if someone can recommend anything else i would also be interested.
Unless you are almost finished or you plan to return to Canada, dont bother with your ATPL cause it means squat to JAA.
Hope this helps and good luck