That for me is not the issue I dont understand how I get 350 to 450Mb/s with the ethernet cable connected and 90Mb/s when I remove it. Also, I dont really want a cable running across my room (or to be more accurate my wife does not) if I can avoid it. I would be most grateful if anyone has any thoughts on this issue.
You aren't talking about the TV Ethernet port or the TV wireless, just the Sky Q box. Is that correct?
The newer HDR Sky Q boxes have a gigabit port and not 100Mb port.
I believe the Sky Q boxes will only connect via 2.4GHz back to the main router, if the main router isn't a Sky hub. Might be wrong on that part, I don't have 1.
That would explain much lower throughput wireless to the Sky Q than to other devices.
90Mb/s should be more than sufficient for watching 4k HDR and running a download in the background on the Sky Q box.