giffgaff recently launched international delivery for 'ordinary' SIMs.
Why not adding the possibility for someone abroad to get a referral SIM sent by giffgaff too?
When newcomers sign up, many websites will usually ask if they were recommended by anyone in the form of an optional field named 'Has anyone recommended us to you?'. People can then enter the name of the affiliate thanks to whom they're joining in. And the affiliate gets a reward.
If such a thing existed with giffgaff, the advantage would be twofold: 1) giffgaff would only deliver SIMs to the Super Recruiters who need them to hand in directly - locally, that is - hence saving quite a lot on shipping costs on the 50-SIM box, and 2) by shipping the SIMs out directly without sending them to a Super Recruiter first, delivering abroad becomes much greener and faster (far less transport involved).
Also, people abroad should be able to order several SIMs at once with a limit to be determined (4 SIMs per address seems about right). This is to ease the job of relatives travelling together.