Just to follow up on my own question for future readers.
Nothing happened for a few hours, and still only one aisle seat (and multiple middles) available, so I tried to see what if I could do anything.

When simply managing my flight, clicking on the Bid for Upgrade option got me to a page saying "no upgrades available" (which my have been that I was too close to the flight to initiate a request)
Then I remember that the confirmation email had a view/cancel/modify link for my bid, so I found that and clicked on it.
At least that go me somewhere so I raised my bid by 5gbp (250, up from my initial bid of 245, which I figured would put me above anyone who bid the minimum 240) - still rated as Poor, but {shrug} .

It accepted the modification though so that was good.

Around around 7PM I got a notification of a charge on my credit card, which got me anxiously checking periodically to see if it was actually live on the site so I could make sure to grab that aisle seat.
Went to bed with stlll no upgrade. Email confirmation came in the early morning hours and when I went on there were actually about 12 more seats available than I had actually seen.
My first thought was a mass migration to Upper, but all seats still showing available up front and I realized that it's apparently due to the "preferred" premium not being visible to me until I was actually confirmed into the cabin. (DL DM/STE+)

So all worked out well - I'll get 3hrs in the clubhouse and a nicer chair for 250gbp.