I have always been a low user of my mobile, mostly receiving calls and after the demise of iSim I was looking for a similar provider.

Kiss Mobile, while the name might be a bit offputting is great, their call rates and deals are setup with something to suit everyone and whats more, their credit never expires!

Even thought they are online only, their customer service is great, always helpful and speedy replies to queries

The only negative I would have is that it uses the vodafone network and its not the best as far as coverage goes.