Brendan @9 Good point, and I'm surprised nobody else has mentioned this. The lower of the two identical letters (4th of 6 down) seems to fit better with the "maps" of the location I've found online, but the highlighted cells are an approximation of the real thing and it's not easy to tell which cell to use. Anyone else have thoughts on this?
This was balm to the brain after last week's grind, despite me making it more difficult than necessary by forgetting about the initial letters and finding the theme by grid staring!