I binned sky and sent sky Q back over a year ago. I still have my dish and they've never asked for it. It never even came up in conversation.
I actually used it with Freesat for a few months. Just plugged the sky leads from the dish straight into the Freesat box.
Note on sky Q box. Keep the recorded delivery receipt when you post everything back. I heard nothing for months. Then they sent me an email stating I had a week to return everything or I'd be billed. I'd sent it back over 6 weeks ago. They denied receiving it.
Fortunately I'd kept the receipt and checked tracking details and it had arrived at sky and been signed for. Dropped the threat instantly. A classic 'sorry we've made a mistake'. Cheeky f*ckers trying to get £300 odd quid out of me