if anyone is already with sky, and are outside of your contract, you can easily get a sky+ box for free.. just phone up and tell them you want to cancel your sky as you are moving to virgin.. obviously a heinous lie, and no-one in their right mind would actually do that, so try and make it convincing..
they will obviously try and convince you to stay, but stand your ground and just say that you work shifts so you are never around to watch all the sky programs you really enjoy, or something.. the person on the phone will probably offer you a new sky+ box for £49, but just tell them "no thanks".. note that
this person cannot offer you a free sky+ box - it is the
retentions team who will do this..
under the terms of your contract, there is a 30-day cancellation notice period, so don't worry - you will not suddenly just lose your sky connection! just stand your ground, politely tell them you want to cancel, and let that be that for the time being.. now just sit around and wait.. about a week before your 30-day notice period is up, you will start getting calls from sky, desperately trying to get you to stay.. they might offer you discount packages, or try and give you free internet or something, but hold out until they mention sky+.. play your cards right, and you can get a brand new sky+ box absolutely free, with free installation..
i did it a couple of months ago, so i know it works.. then they tried to charge me £50 "moving fee" to install a dish at my new house in stafford when i moved.. i told them to take the whole thing back and i would go with virgin.. surprise surprise - they apologised and offered to do everything for free
note that there are no longer different capacity sky+ boxes on the market (i.e. different hard drive sizes).. all boxes are now 80gb, as the larger capacity ones were prone to crashing all the time..