Just a bit of advice from my own experience, even if I'm a bit late to the party and lots of good advice had already been given!
Mobile Phones- Depends on what kind of phone you have. As has been mentioned, it's all about SIM cards here. I brought my Razr2 from Canada, thinking it could just be unlocked and get a new SIM, problem was, no SIM! So it does depend on the phone. The thing here is, there are SO many phone choices at so manyt plan options and cost options, getting one here isn't a bad idea.
As for specific elctronics, I'd say only what you need and at that, don't forget to shell out for adapters and whatnot. I brought 3 external hard drives, a little clock radio/ipod speaker thing (which not too surprisingly pics up a couple BBC stations), and that's about it. Since you're not moving here permanently as I have, you'll likely want to bring more of your own stuff, I would think. A laptop though, for example isn't THAT expensive to buy here for a basic one but if you have an adapter AND a converter AND are really attatched to yours Canadadian one, that would work too. You can get adapters here in England too.
Food- I've had some of the best pizza I've ever had in London! PapaDel's in Highgate, for one (with good prices as well), and any number of Italian places, as has been said, and there are a tonne. Dominio's is here, and is the same more or less, yes and the supermarket pizzas are pretty tasty. I've found much of the food here to be richer in general. Not necessarily more sugary or fatty, just....fuller. Hard to explain, even the Hellman's mayo seems to have a little something that it didn't in Canada. One thing I found was that depending on where you are, it can be hard to get a NON instant cup of coffee (assuming you're not near or don't like a Starbucks or Cafe Nero). That was rough when we first got here, where we were staying (Lewisham) had nothing like that, it was awful. I like tea but in the morning, I have to have coffee, so I moved next to a coffee shop!
One more thing on coffee, there is a Canada Shop in Covent Garden in London (canadashop.co.
uk, I think, or something like that) that has a small selection of Canadian food, Reese's PB Cups, Pancake mix, etc, BUT, has a place for TIM HORTONS COFFEE. They still had some cocoa mix there but naturally, the coffee was sold out!
There are plenty of sushi restarants that are amazing as well, a good rule of thumb (as with Shwarma) here is, if it looks dodgy, it probably is. One thing though, good sushi here is not cheap. You can go to a 'Wasabe', which is a take away, pick your own type place that's pretty cheap, but you get what you pay for.
Hope that helped and your moves have gone well to those coming over.
GB