It used to be you could not sign up again for SKY within 6 months after cancelling regardless of the name you use.
Not sure if that is still the case so if you're considering cancelling then signing up again it may be worth checking.
Or, if you could live without HD, you could get a moody box and a 12 month sub for the price of maybe 2 months sky tv.
Personally the only difference i see between HD and SD is HD looks brighter.
That could just be me and i could have shit eyesight though