i have a completed grid and also have found the 26 letters. I can't find the penultimate misprint and can't fathom the wordplay for 42 across and 33 down. The connection between the 26 letters and the discovery of JA also totally eludes me. The other site seems to think it's funny.
escuan - use the previous hints to find the connection. They were enough to get me over the line. You are looking for three place names in a circle round the edge of the grid. Personally I didn't see the joke!
Escuan, some on the other site think it's funny. Most don't.
Unless I've misunderstood something about the theme, to me the preamble is just inaccurate, and one might say unfairly misleading. The arrangement is NOT thematically placed at all.