Thanks for all the answers!
As soon as I arrived at T2 and saw the Star Alliance branding and had a "Oh.... that...." moment.
Security was speedy, and I used my Priority Pass to go to the Plaza Premium Lounge. For a lounge with no windows they've done well.
The Flybe flight was fully booked - as were most of yesterday's flights to Edinburgh - unfortunately and I should have seen it coming, we were bussed to the aircraft. At Edinburgh we were bussed from the aircraft. Overall the train would have been faster, but price won out.
Flybe are a decent airline - have always had nice flights - bar one from London City to Inverness which landed in a snow storm and I thought I'd met my maker!