Hmmm, I'm not sure Film4hd is needed.
If you have sky you can watch film4 on channel 315 but how many times have you watched it? I can honestly say I havent watched it once this year so I doubt having it in HD would change that.
Also if you compare Film4 to any other SD channel then you'll notice film 4 looks VERY VERY good. Its like Sky deliberately upscale film4 or use the HD feed. But even in HD I will never watch "How to marry a millionaire"(1953).
Life is just to short