You can get your regular 5 channels (bbc 1, 2, itv, ch 4,5) and all the other garbage itv 2, bbc 3, 4 etc etc etc......
Basically you get everything Cable broadcast except the pay per view movies.
It's not a subscription - you buy a box (from Germany), replace your old box with this one and you have a little more than what you started with.
As Simon_d says - it's also a faster box at switching between channels. I reckon it's worth the £117 (delivered) just to have a faster switching box - let alone what else they do!