on 05-10-2013 11:41
Yes, they do. And if you need to change your sim for one, there's a process in place to do just that. Sim swap.
Order yourself a Nano sim from your spread giffgaff page.
Once it arrives, follow this guide for Sim Swap:
All of your account info - goodybag, credit, user name, mobile number etc remain the same on your new replacement sim.