I’m only familiar with the DG vinyl, which I picked up some 45 years ago. (I wore out the vinyl years ago, though - I now have a CD with Brendel playing with another orchestra.) The Berg concerto wasn’t included, just Schoenberg’s Violin Concerto with Zvi Zeitlin doing the honours as soloist. After checking on Amazon, I see they had Henryk Szeryng as soloist on the Berg concerto. That sounds familiar: I may have it kicking around on a different compilation.
Brendel’s performance with the BRSO is on YouTube, however: