You'll be connected via a Talkmobile SIM, a network which, we seem to remember, uses the Vodafone network infrastructure.
Someone will pop up in the comments saying you can get an extra £30 refunded to you if you use the Quidco cashback programme, too. We've still not bothered signing up for that, though, as we're trying to cut down on luxury consumer goods purchases.
Link via HDUK and reader k0zmik.
source: Eurodroid