Minimum to watch F1 on sky is £30.25. £20 is for Sky entertainment only which doesn't get you F1 channel, so you need to pay the £10.25 extra a month for HD, which will get you F1. However for £5 more you get the entertainment extra pack, which has 90 more channels compared to entertainment only. So £35.25 a month for 90 extra channels on top of the freeview channels + HD content. That includes Sky+HD box and installation.
Expensive, but at least I get F1 with Crofty and Brundle, all my fav programs in HD and a bunch of car and motorsport dedicated channels to keep my entertained, as well as a load of documentaries.
If however you don't watch TV as you said it's pointless paying all that money for only F1. Sky are a rip off at the end of the day, but I just can't do without F1.