There is a guy on ebay reselling ekit's SIMple Calling Plus Service for $8 [ouch, for Canada he wants $10.00 shipping vs $3.50] :
SIM Card (item 140399251599)
This could give you one SIM for your whole trip. It also works in Canada and the US. [look up rates.]
The SIM has a US and a UK number.
All four of the countries are Zone1. A 35c connection fee applies to each call made (from all Zones) or received (outside Zone 1a & 1b).
There is a 19c per minute surcharge to receive calls on your US +1 number in all countries. Calls _to_ your UK number in your 4 countries is free.
Study the rates and see if this works for you.
On second thought, for you as a Canadian, seller ekitmobileusa has the same card for $9.00 + $5 postage to Canada.
You might send a message to the first seller about his rate to Canada and if it is adjustable. I have purchased one of these SIMs from this seller and verify that this is what it is.