It was a close thing.  

I managed to save a few pages but eventually gave up as I am simply not fluent
enough to understand the command line stuff or how to organise the exceptions. 
I would need to do a proper course in that kind of thing to be able to
download the pages I needed and exclude the ones I didn't, and sadly that
would take longer than the few hours I have left to save an archive of four
years' worth of discussions.

Thanks for creating the software anyway and for the very helpful advice that
almost allowed me to achieve my aim.