Allow users the option of receiving their payback via bank transfer.
It’s much more convenient and accessible compared to PayPal, and would work better for those under 18 (GiffGaff lets you get payback at 16+, while PayPal is 18+).
Furthermore, GiffGaff’s excuse on this matter is that they would have to set up a relationship with every UK bank. This is categorically un-true. A business account at any bank would let them send payback via BACS or FPS to all of us - with even less effort than PayPal.