The best way around this is after the 12 months say your box goes faulty , Cancel your Sub & then get someone else to phone up in the house hold and order sky in there name... Iv done this with my brother and it works
Ah, not always I'm afraid! They usually won't supply you if the box is in the same surname, so I think you were lucky if your brother called up! They refused to install a box in my girlfriends name after I cancelled at our address, as they knew it was still the same residents at the house. We weren't trying to pull a fast one, just trying to re-subscribe after it had been cancelled. They upgraded us to HD fine though
If the box does fail, either pick one up from ebay or just call up and ask for a replacement. Regardless of whether or not you feel you're entitled to one (and I'd agree you should be) lying about moving out is still kinda fraudulent 
Actually, I'd just go for HD for £75, then you have a 12 month warranty on a new box and HD! Far superior to Freesat IMO.