Hello

I will definitely go down the option of different installs, and link to different CSS files.

Each installation will automatically have it's own CSS file.

Therefore there's just one last question: Once installed in a different folder, would it then be ok to amend it so that the install then links back to just the one set of the other folders, i.e - lang,themes,modules,etc - rather than have a duplicate set for each forum, so that I have a 'neater' file structure.

It is safe to use the same language and (external) modules files/folders if there are no differences between the installations. You can use a single base for JavaScript files too (folder js). Different to that the themes folder contains the CSS file for the installation. And yes, that could lead into trouble.

Tschö, Auge