Lebara's good,a bit cheaper than a sky sim.We had no problems with Lebara
My Lebara sim is Vodapfone,it's a good sim.Lebara is on Vodafone I think Bill so as Jann above recommended it also it sounds like it might still be the case.
The very quick search I did reported many saying that it was a lot slower than Vodaphone. Let's face it if you are piggybacking on a carrier the carrier will keep the best for themselves. Or so I would think.Lebara is on Vodafone I think Bill so as Jann above recommended it also it sounds like it might still be the case.