Thanks for the further comments and suggestions.

Having tried calling twice more and 'management' (presumably revenue management) having formally declined the emailed request from the call centre to 'move' the seats I have given up.

Seems a shame BA are not a little more customer focussed. I am not a particularly frequent flyer (maybe 6 return flights a year with BA) but they are not working very hard to help their customers work with their somewhat limited self-service booking systems.

Clearly they could move the seats if they wanted to (even if that involved someone in the back office taking 2 minutes to generate 4 new seats and cancel down the original 4) but obviously the focus is profit, not customers...

Unless anyone comes up with any other suggestions (or a customer friendly point of contact I could approach) then I guess my only option is to watch carefully for additional return availability to open up.

Thanks again!