If I buy a Sony laptop from Canada and take it to Britain will its warranty still be valid?

Likelyhood no, becuase you are going to have to take it over here and use it on a british power supply, therfore causing you to use an adaptor, or modify the power pack and put a british plug on it, don’t quote me on that though, contact them and ask for yourself…

If you are a Canadian citizen and the laptop has an international warranty, yes.

If you are not a Canadian citizen (regardless of whether or not the laptop has an international warranty), only if you send the laptop back to Canada for service.

International warranties on laptops are only valid outside the country the laptop is bought for citizens of the country in which the laptop is bought (they are valid for anyone inside the country the laptop was bought). If you are not a Canadian citizen you’ll either have to pay for local repairs out of warranty or have it sent by air freight to Canada for warranty repair (you’ll have to pay for freight both ways).