Giffgaff have today announced 3 data-only goodybags which will launched early next month. They can be used on your phone as normal or for tethering/dongle use. The 3 options are:

500MB for 5
1GB for 7.50
3GB for 12.50

The third option is clearly designed especially for tethering/dongle use, because as we know the standard 10 goodybag already offers unlimited mobile internet. All 3 goodybags have a 50MB 'buffer zone' which can be used in addition to the stated allowances without extra charge. Beyond this, the charges will be 2p per MB until the expiry date of the goodybag is reached.