I have a full grid but haven't started staring at it yet. I thought I'd try adding the clashes but I seem to have gobbledygook - including a Q but no U. I take it I am wrong somewhere?
Planks, you add the letters’ positions in the alphabet as usual eg C(3) + J(10) = M (13). BUT 27 is a space so if the sum is greater than 26, eg T + Y = 45, you subtract 27, not 26 as you’d usually do. Hope that makes some sort of sense!