what differences are you re referring to - HD channels and UHD channels?
no- offence given but do you have good eyesight 20/20? as resolutions get higher its harder to tell the difference between em, ive got 20/20 and can just tell when Netflix moves from 1080 to 2160 as i have an info button that shows me the bitrate and resolution.
also, sky is crap for bitrate stuff. (always low)..i know the now TV app is 720p only - Netflix is amazing for 4K - try 30 days free on that and watch OUR PLANET just for pic quality - best in the world as is PLANET EARTH 2 as these are NOT movies and so haven't had as much processing, not dark, and full-color spectrum, always bring out the best of a 4K TV..just so you can see yes your TV is brill so anything crap is NOT the TV.
personally, have not used or watched anything on Sky Q or their UHD channels but a LOT of stuff these days is pseudo 4k, that it has was shot 2k-3.8K then professionally upsampled to 4K, some stuff even shot in 4-6-8K still have 2K digital intermediates which mean the 4K is again an upscale , but slightly better as the quality of pixels is better (better capture to play with)- to know if your watching stuff shot on higher than 4K cameras and has a 4K digital Intermediate (what ALL discs are made from) and thus the UHD Blu-Ray will be true 4K is to check the technical specs of the movie on iMDB technical specs section of the movie page check the camera resolutions used and where it says digital intermediate near the bottom is what your looking for.
Older movies from 20+ years back that where wholly shot 35 or 70mm are ok(ish) cos 35mm was said to be good for about 6000 lines of resolution (6K) - BUT in my experience and having seen hundreds of 1080p 35m scans and several 4K 35mm scans, I don't think 35mm IS good for 6K, I think 35mm''s digital scan limit is 4K as grain start to get heavily introduced...even on 4k on some films have a lot of grain...it all depends on
1) quality of film used (as in good brand, cheap brand)
2) the actual 'quality' of the celluloid itself as after years it starts to degrade
I watched Batman in 4K from 35mm and it was no better than 1080p in my opinion, like 1080p with sharpening 100%
so I use the method above to see what it is im ACTUALLY watching
I would NEVER rely on sky for UHD pic quality, I used to work for sky...they just want your money. always had people complaining about pic quality - Virgin probably won't be much better either.
ive watched a handfull of 4K stuff and documentaries are what truly bring out the 4k on your TV - movies not so much - imo
there's the whole "ah but the CGI is always done in 2K anyway" - not always the case and due to that type of technology upscaling is a WHOLE DIFFERENT MATTER, because CGI worlds/things are generated in 3D and can be as big or small as you like, with extra detail shown on close ins.
Its new movies from 2000+ that suffer the most (shot digitally usually ending in a 2K DI) as movie companies aren't so bothered about the quality or how it was captured, just as long as it has that 4k UHD badge on for resale for the 4th time (|VHS-DVD-BLU-RAY-4K)....AS CHEAP AS POSSIBLE