Final Update - After contacting several aftermarket Auto in-car entertainment specialist outlets I decided that the cost would be too much. Some Pioneer units were coming-in at over £2000!
I contacted KCS through this forum and they confirmed that the warranty for in-car units was 36 months/60,000 miles but they also gave some encoraging news that they do an "exchange programme due to the cost of these units, regardless of age or mileage but as long as there is no damage from external influence and the dealer diagnose an internal failure".
So booked in to Snows of Guildford where their "tech" guru, Dave, was able to diagnose the fading screen as an internal failure. Both he and Katie ran me through the options and confirmed that replacement units were available.
However, the bad news was that they had to be ordered-in from KIA and that could take upwards of 6 months.
So here we are just over 1 month later, and I have a replacement, fully working, original head unit.
AND the good news was the cost, .......... absolutely NOTHING. Now that is what I call GOODWILL
Thank you Snows of Guildford, Katie, Wayne and Dave and thank you KCS. I can go forward now, knowing that the EV6 massive infotainment and control screens will have some backup. I wonder how much those Tesla and Mach E screens would cost to replace?