Unfortunately, you sometimes get flicked a long way back. So, I pre-assign myself the front of ET (usually C, not A, and never D, E or F) with 'informed risk' so to speak because I know I could get seat shifted to somewhere I do not want to be and potentially a long way back.

My new discovery (yes I know, I was a LHR-routes girl, but now doing more LGW routes) on 737 is row 5 which is often the 2nd row of ET but still without the B seat. My (possibly uninformed) thought is that by picking row 5, there is less chance of being affected by the curtain shift.

The funny thing is that I have picked those seats often but still have not travelled in one yet. That's not due to BA seat shifters; it is thanks to paid airport upgrades at LGW, often available even when MMB does not give me a POU option at a decent price.