Yesterday O2 announced they were simplifying the data add-on and tethering options on all new contracts (or upgrades) for its customers.
There are now 3 simple data bolt options – 100MB at £3/month, 500MB at £6/month and 1000MB (1GB) at £10/month. The top 2 tiers also include free unlimited WiFi usage at BT Openzone and partner HotSpots which should tide you over until the O2 Free WiFi service starts to gain coverage.
The real bonus is in the the tethering option however, which previously used to cost £7.65 to enable, but is now included for free! This includes the enabling of the Personal HotSpot feature recently built into the iOS4.3 update on the iPhone and iPad.