This puzzle has been a bit of a relief for me—I've spent several days on it so far, but only a couple of hours in total, which is a change.
My grid is about 90% complete. I also have the full reminder (idiotically, I quickly forgot to apply the "across" part of the preamble; eventually it started seeming suspicious that I had no confirmed extra letters in the downs), the name and awards, and (I presume) the principal unclued entry, to which I have not yet determined how to apply the reminder, nor have I yet highlighted anything.
Despite having the full reminder there are a few letters in which I'm not sure how the letters are derived. In most cases this is because I simply haven't worked out the wordplay at all (38ac, 42ac, 43ac), but in one case I'm particularly confused because the clue seems to be complete in definition and wordplay as-is. That is:
20ac: Opinion about bridge player became stale (5)
I'm inferring this needs to have a substituted letter based on the other letters I have adjacent to it, but I'm not sure how—especially given the letter it appears to need to be. Any nudges?