Many people seem to be confused over SKY box ownership (probably because of the cable and sky similarities). So I thought I would do a brief summary.
If you get SKY TV installed (so a dish fitted with a SKY box or multiple boxes for SKY multi-room) you are contracted to subscribe to SKY for 12 months.
After the 12 months is up the equipment is yours and is out of warranty (so even if you still subscribe if something goes wrong you may have to pay for a new box or a repair)
After 12 months you are free to cancel your SKY subscription - you will still be able to view all the freeview and and most freesat available channels
You do not have to return your Sky viewing card - that will be switched by Sky to a freesat card automatically once you cancel your subscription (if you have a very old card you may have to pay £20 for a freesat card - see my other guide here: Get WHITE SKY VIEWING card info free + more channels
If you choose to upgrade to SKY HD or SKY+ from an old box they should not take your old box away - the old box is yours and you can keep it to sell or use in another room. Some naughty engineers try and take the old boxes because they can sell them on.
Since new subscribers get better offers than existing Sky subscribers sometimes it is better for you to CANCEL your Sky subscription, wait a month then sign up again as a new customer - since new customers at the moment get a free Sky HD box and free fitting but if you are an existing Sky customer you have to pay £60 fitting??? Then when the engineer comes out to fit your new dish and box he will have to take down your old dish then you have your old dish and box to sell on.