Swap SIM for new phone

[Arby]

I have a 'new' phone (iPhone5) since my last visit to the UK and need a Nano Sim. I want to be 'up and running' when I get to Heathrow and am wondering if there is a store at Terminal 2 where I can swap? Would appreciate any advice

[kids]

There is a Vodafone kiosk as you leave arrivals in T2