Hi lewisid69 and welcome to FlyerTalk!

If you're planing to travel in the near future, you probably wouldn't need an exit row seat as the loads would be light due to the Presidential Proclamation on the US side and the 5-day self-isolation + testing requirements on the UK side.

Otherwise, it's unfortunately true that on BA metal, oneworld Sapphire members ( including BA Silver ) does not get free exit row seating on long-hauls. However, at OLCI, it's free for oneworld Sapphire members and in case the exit row seats are blocked at OLCI, you could ask for them at check-in.