Dave,
I know the gig you're talking about.....I was there! It was during the Tormato tour and they did a couple of nights at Wembley Arena. I remember it as one of the best Yes gigs ever!!!! They did a FANTASTIC medley which lasted ages and included Time and a word, Long distance runaround, The Fish/Survival, Perpetual change and Soon.
I haven't seen a recording of this gig although I'm sure there must be one out there somewhere. However, I did pick up a copy of a double CD at a record fair called "TOURMATO (PART 1+2)".
It 's from a gig in Vancouver coliseum on 5/5/79 and is practically the same set. Recording quality is good/v. good.
Hope this helps you.