I’ve heard people say that they have ordered SIM cards for their friends but their friends don’t bother activating them.
If there was an option to pay for credit with a voucher before the SIM is sent out, I think this would eliminate this problem. There could be a box on the ‘Order more SIMs’ screen saying “Type your 16-digit voucher code here to activate your SIM before we send it to you. (optional)”
I have already considered the potential problem with this idea: “What if the SIM doesn’t arrive? Do I just lose my £10 voucher?” Keeping this in mind, there could be another box under “Type your 16-digit voucher code here to activate your SIM before we send it to you.” This box can be for a password which you need to type in to fully activate your SIM. This means that if the SIM gets lost in the post, the person who finds it can’t get your tenner! If you don’t receive your SIM you can tick a box saying “SIM not received”, so giffgaff can cancel the original SIM and send you another SIM using the same voucher to put your £10 on.
I apologise if I have rambled on a bit, but I just wanted to show that I think I have found a way of making this idea work!