There is no 4K content using Uk C/S, regardless of the box or TV you use.
My dad has a new 4K Sony TV, the picture quality is the same as his old 1080p TV.
You need a genuine sky or cable subscription to see any benefit, unless you stream 4K content off the net.
He has an Ultra HD Netflix account but it's still not as good as the picture quality from the HD channels using cable C/S.
What you get out is only as good as the signal coming in usually 1080i or 1080p tops.
The picture quality in the showroom doesn't reflect the picture quality most people will be getting in their homes.
Sorry if this bursts your bubble but do you need to shell out for no improvemet ?
I know my dad expected the picture quality demonstrated in the showroom at the time he bought it, but this wasn't explained to him, but why would they ?