Wiggly, I signed up with BT for their free call weekends at £11.75. Then they reduced it to £9.99 and added evenings also. I think this is a good deal. Connections are pretty quick but I have to say that the speed drops a little in the evening. Well you can't have everything if the world and his wife are on can you.
BT plan to do a new deal in June I think, for £5.99 for as above BUT you will be able to use any ISP you wish - now that is bloody good in my view. However, BEFORE then I reckon someone will come in with something that will blow your socks off. Bound to happen some time. My bet it is that it will all be free within a year.