Tesco Sim Card - £10 - good coverage?

[LadyBubbaAndBump]

Anyone used one of these? I'm assuming they sit on the back of somebody else's network but don't know, and dont' know how I go about finding this out here

I get fine coverage on the SIM-only plan - they use the O2 network.

Thanks ByTheSea - that's who I'm with currently, but this Tesco deal looks like a steal! :)