Well, finally managed to get W.Bloggar working from work. Seems it really doesn’t like the NTLM proxty we have here and isn’t providing my username/passsword correctly.
Thankfully found this post pointing me at a piece of software which does just what I want – it acts as a pre-proxy proxy. Its called Ap Server (don’t ask me why) and uses Python so should work on pretty much any platform.
Lovely! Now I’ve just got to work out how to easily configure it to work when I’m at home (no proxy) without changing 23 different configuration settings.