I'd certainly bring it with you as probably most British people (if they've heard of it ) think it's some kind of chocolate spread and therefore a luxury rather than the secret behind Italian sporting success. We generally bring back a 4kg Easter special jar but missed out on going this this year.
While Nutella is available in UK supermarkets I wouldn't want to promise that what's sold here is the same as is available in Italy as some European food manufacturers make special (added sugar/fat, lower-cost ingredient) versions of popular european foodstuffs for the specific tastes of the British market.
I have a local jar here. It's claiming Sugar, Vegetable oil, 13% hazelnuts, 7.4% fat-reduced cocoa
55% sugar
31% fat
6.8% protein
530 calories per 100g.
Hope this helps