I have been informed by a bloke who works for sky that the way they encript the channel only works on modern kit. if you have a really old video recorder eg: Ferguson Videostar they are unable to pick up the new fangled encryption stuff and record as normal.
I have not tried this. So can't vouch for the reliability of the information but the bloke seemed to know what he was talking about. I do have an old 1980's ferguson video recorder and I will get around to trying this out one day.