PiperUK
Having ben through exactly this (not happy with picture from Sky+ machine connected to LCD via scart) and having exactly the same situation (pay 10 a month only for Sk+) I thought I'd do the experiment so I bought a Sky HD box from ebay and plugged it in. I thought, well even if I just get the extra disk capacity and the HDMI connection it'll be worth it. I'm pleased to say that it all just works as I hoped it would. I get BBC HD and Channel 4 HD. I can record programs. I get Five/Five US etc (which you don't on Freesat Not From Sky). I get BBC interractive services (which again you don't seem to on Freesat Not From Sky).
I just took the card out of my existing Sky+ box, stuck it in the Sky HD box, swapped the cables over and bobs your uncle. The picture is definitely better, even on SD, so it's definitely worth it for the 150-200 quid you have to spend to get a Sky HD box off ebay.
Until Freesat has more channels (namely Five/Five US -- I like House, the wife likes Neighbours/Home and Away 🙂 ), and until a decent range of PVRs, DVD recorders etc is available for Freesat I'm sticking with this st up, even though it does cost me 10 pounds a month. Currently no alternative that fits my requirements.