There's no shortage of mobile networks to choose from in the UK, but that hasn't stopped the Post Office from throwing its hat in the ring. The iconic mail service is launching a pay-as-you-go SIM that focuses specifically on cheap calls and texts. At 8 pence for almost any domestic landline or mobile, calls are significantly cheaper than the standard rates set by Vodafone, O2 and Virgin Mobile. The new "virtual" mobile network, which is powered by EE's infrastructure, is also competitive on the SMS front with a flat 10 pence rate. If you're interested in data, however, you'll probably need to look elsewhere. The Post Office charges 10 pence per MB and currently doesn't support 4G connectivity. Even if you're a light user, one of the company's 30 day bundles is almost certainly better value.