I love giffgaff, but the coverage into area (north east of Scotland) is terrible. I can't get 3G at my house!!
This is appears to be due to limitations in the O2 network coverage.
My idea: talk to other network suppliers and offer customer the option of giffgaff (O2) or giffgaff (3) and so on.
Or or even better - allow your users to automatically connect to the strongest 'partner network' at any given time!!