>>> I have never been able to see why they don't get the best professional artists / singers from each Nation to go against each other !
Because such an artist would need to take a week out of their touring schedules for the semifinals and final (together with all the rehearsals prior to those performances), plus spend time promoting the song in the weeks beforehand. The likes of Ed Sheeran would demand millions of pounds to do that, which broadcasters simply can't afford to pay. Michael Rice is a lot, lot cheaper!
Anyway, it's meant to be the song, and not the performer, which is being judged. Perhaps the selection process needs looking at? (We've tried most ways and still can't seem to get it right).
Personally, I'm never in the least bit bothered about whether the UK comes first, last or anywhere in between. I watch the Eurovision Song Contest to enjoy the programme as a whole and to support the song(s) I like best, irrespective of which country has entered them.