Order new sims here
Or Order a new SIM from your Spread Giffgaff page https://giffgaff.com/orders/mgm
New GG Sims are all sizes now and are 3-in-1 sims, standard, micro and nano sim size, the smaller sims pop out the middle
Giffgaff sims are posted out 1st Class, so should arrive within 1-3 working days.
and when it arrives / you are ready to change, do a SIM swap
you will then keep your current number, credits and/or goodybag. The swap should take no more than 30 minutes but can take up to 24 hours