You won't be able to get jello from a shop here, unless you were to find one that stocked American products. There are a few around, it might just take a little research to find one. Usually I buy online for things like that.
Your question got me looking, and I've found some SF chewing gums with great pudding flavours that I forgot all about! (Mint choc chip, Key Lime Pie, Apple Pie etc etc) I shall be buying some of these come payday!
Ive only ever seen jello in the USA. Pity because there are so many more flavours than Hartleys sugar free jelly, which is found in tescos & waitrose. I buy the sachets of the powder not the ready made stuff as the latter has fruit in it. I like the orange, raspberry and the strawberry, but they also do lime and blackcurrant.