If you had asked the public the question in 1990 then the top three answers (in no particular order) would probably have been Thames, TV AM, and UTV. If that was the outcome then the fourth most popular answer would have been a very distant fourth.
If you'd asked the public, they wouldn't have even heard of UTV (or even STV for that matter) for the most part I'm sure.
More likely the answers would have been TV-am, Thames and Granada. At the time Granada still had a reputation for being PSB-focused and very tied to the "North".
Depending on where you lived, I imagine many people didn't know the names of most of the ITV franchises apart from their own and the ones in the neighbouring areas. Seeing end boards from TV shows might have meant production companies to them rather than region names.
True, but the big 5 were names very much in the public conscience, as they saw the endcaps (and frontcaps a couple of years previously) every day. The smaller stations would not have registered unless the name was obviously tied to the area it came from (and 'Ulster' would have been cryptic to many more ignorant members of the public despite the very clear meaning), and the very small stations won't have even registered with people.
Yes, if people were made to sit down for ten minutes to see how the system worked they might have come to the conclusion that UTV was the potential stand-out, but even that would depend on an understanding of NI politics which, as Brexit has demonstrated (sorry Asa but it is a relevant point in this case) many in the mainland simply don't have.