It's back again tonight in a limited way, no First Class but Business Class is $1769 GBP for variations of INV-LHR-SEA and you can add GEG, PDX, BOI etc on Alaska. PDX also allows SFO and DFW connections for 818 GBP each way. First Class comes in at 7292 GBP. This is for a Feb-May 2020 timeframe but it goes on into summer for selected dates. It comes and goes so if it isn't there when you look, wait about 15 minutes and it will probably return.

The first night that this returned and the OP posted, I tried for hours and finally booked EDI-LHR-SEA return for $1763 GBP, first class outbound, business inbound. It took a long time and the BA website kept kicking me out on the submit payment page. Then a couple of nights later around midnight I snagged CAI-LAX-CAI business in October for around $2300 USD. Don't know if that is a bargain but the "regular" price this year seems to be 6-7K for that route from the U.S. I haven't been able to log in to FT for unknown reasons until tonight but the CAI flights seem to be still there.

A question about where to post these miles: I have no status anywhere and originally planned to put them all on Alaska Mileage Plan with the goal of getting enough miles for a Cathay or JAL Business Class flight to Asia next year and maybe getting MVP status. However, if BA Silver is good enough to get lounge access in various places, that would be useful too. I'd be interested in hearing any opinions on that subject.