Nope..!! "Wild Side of Life" definitely WAS released in Britain, and entered the charts, and I can prove it because I still have the vinyl single ( !! ), as I thought from day one it was one of their best and most under-rated songs..!! Can't think of any other one not released in Britain, although there were plenty not released in America..!! :o)
I think there's more than one. Technicolor Dreams is one possibility as this was pulled from UK release at the last minute. I think Don't Waste My Time (one of my favourites) is another not released as a single in the UK. Go to the excellent http://www.status.quo.btinternet.co.uk/
for all the info you need.