Thanks very much all, and ta for moving the thread Jimbuna.
The test chart to see if it all actually works has just arrived, and I'm about to give it a whirl.
The font is a digitised version of the historic Kriegsmarine chart typeface, so almost identical, and the compass roses are all hand drawn (well, with a mouse) - I only have myself to blame if I plot the wrong course...
First lesson learned is that most elements are about almost double the size they should be - it would have been the perfect resolution for A1 rather than A0. Either way that's easily fixed.
This is by no means the final product, and with the invaluable help of Pino from Kartengruppe.it I plan to get the smallest historical details included. This applies doubly for recreations (or rather SH3 versions) of real charts.
Just about to put on my Obersteuermann's cap on to test it out in a "hotseat game" (3-4 of us with various roles)...
Here's a few shots of it with a bit of set dressing (and under red light):
Ah, just a bit too big
And a slightly blurry shot of the whole chart.
Pleasantly surprised at how crisp the in-game screenshots I used to build the map itself came out. I'm still planning to redraw it all for the final version though.