Originally Posted by
atsak
Agreed to buy one when you get there. There's apparently vending machines in LHR and other airports; I was in Manchester and saw a mobile phone store right in arrivals the other week.
It takes about 5 minutes to do the whole thing and top up at the same time and you're good to roll.
Honestly, I would just have your taxi driver stop at the newagents on the corner of Bath Road (the A4) and the A312 (Cranford roundabout), pick up a SIM and a Fruit and Nut bar.