Originally Posted by
stut
You're unlikely to be able to get a SIM that covers both countries particularly well - while UK SIMs will have European roaming, this may take some time to enable, and is not wonderful value, even if the prices are now capped by EU rules.
Actually, I think
EE's new PAYG roaming tariffs look rather appealing; at £1 for 20MB/day or £3 for 100MB/day of data in many EU countries, it's easy to grab a SIM in the UK that can be used with relative ease on the continent.
It should be relatively easy to have a SIM sent via post to wherever you're staying so it's awaiting for you on arrival, to pop in to any EE shop and have them help you get set up, or to grab one on eBay and have it shipped to you at home before you leave (a quick search suggests you can have this done for C$2.99).