It gets worse...
My punish-the-customer £200 LHR-EDI domestic return fare not only comes with no pre-assigned seat and no priority boarding but no automatic Fast Track either.
The app is issuing HBO boarding passes with no Gold status showing - just plain white, no Fast Track bar code. I queried this with the Gold line and was told that it was because it was a "cheap"

HBO fare and that if I wanted to use the Fast Track I could show my Gold card or get a new boarding pass printed at the airport. My experience of T5 Fast Track is that they won't let you through unless you boarding pass is clearly eligible (i.e. Fast Track bar code) - waving cards around won't cut it. so that's another 5 minutes I'll have to waste by begging for a proper boarding pass. Of course, it is possible that the Gold line have got this wrong but she seemed fairly certain that it was to do with "the recent changes" and that I'm not the first to experience this.
When I did check in, most of the seats were unavailable - presumably because they've been automatically preassigned, so the idea that you can simply select whatever you want at -24 is a myth.
They've also enhanced my 767 into an A32x of some kind.
So, with 12 hours to go before the flight I can still pay less and book EasyJet, including a £3 seat reservation fee (compared to £10 on BA) that gives me:
* choice of seats cf no choice on BA
* priority boarding cf none on BA
* better legroom than BA
* the opportunity to arrive on time cf never, not once ever on BA1464
* and since they've shut the LGW F lounge...