BA's policy of musical chairs is most frustrating. But with an ExpertFlyer aircraft change alert set up for each flight (which picks up any changes to configuration, including any move of the curtain), the problem can be lessened.

It mostly affects me when I'm in the 'cheap seats', as the curtain seems to move around like a yo-yo - but I have had issues when I'm in 2D/F or 1D/F on a LGW based aircraft as some of that fleet have row 1 on the RHS whilst others do not.