I assume you have to have a running sky contract to use the features of sky plus?
You can have a £10 per month standalone (so no extra channels) subscription to "enable" the Sky+ features for FFS viewing...
or alternatively, you could buy a 160GB TopUp TV box (120hrs vs 40hrs on Sky+) for £39 and use that with no subscription and Freeview/Freeview+ (which in many ways is better than FFS, in other ways not so). Sky+ is amazing, but unless you already have/want a subscription to channels, its not so good.