THanks for recommending I check ticketing - done that and I do have the appropriate e-ticket receipt so all seems OK on that side.

LTN Phobia I was also very surprised! But pretty sure it's not an equipment swap as I'd seen the seats at the start of the week as well and availability was v low then too.

Basically, I needed to be on this flight and wanted to use avois, but there were no seats available on Monday, so I booked a rather expensive revenue J ticket. Even on Monday it was the busiest J cabin I have ever seen, with every A/B/J/K seat gone, leaving only lower deck aisles in the centre section.

Anyway, to my surprise avois seats opened up today, so I snapped one up and had my TA refund the revenue booking.

Going to call GGL now.... a middle seat downstairs would be a bummer, but with three consecutive J-F upgrades on BA recently I won't be complaining