imo it's not worth doing so
first of all SOGA covers you for 5-6 years for stuff like this when bought from a UK retailer, as well as having the normal warranty, etc. i know this because i got £55 for my ps3 which failed 5 years and 10 months after i bought it from the retailer, without an engineers report, if i had a report they would have given me £110 which is the cost of a refurb from sony when a console fails outwith normal warranty.
also you need to remember voltages are different, so you need a converter, again another added expense on top of the console and they won't be 100% efficient, etc, etc so over time it will cost more to run, etc.
third is shipping, getting this shipped will cost a lot of money, especially if you want it packaged and insured properly. a lot cheaper to buy one on holiday and bring it back with you, but then you need to declare it at customs, etc.
basically your much better off just paying the extra £50 and buying it here, especially since it's only £349 in the first place.
also the US price of $399 probably does not include sales tax which is added at the till. so the real price of the console in the US and Canada is actually a lot more.