Scarlett,
You need to find the prison and refuge first, then set off to column shown by letter in centre of prison, i. e. the first waymark.. and so on.
I don’t have a Z for the most famous one...
I think I’m struggling as only have 10 of the 15 extra letters. Have full grid but lots not fully parsed. Maybe extra letters in 27a, 2, 6, 18, 19, 29, 31 down?
sounds like you are thinking of the correct prison ..you need another name for it ...5 letters with some roman numerals
I haven't got all the extras either but i have N in 13a, T from 15a, I in 28a, N from 30a (i didn't have an extra in 27a ...thought the answer was just austrian/german for home??
E in 40a
Y in 8d
R in 13d
A in 16d
A in 18d
K in 29d