Thanks chaps, that is great advice to help me finish the job. I knew you wouldn't let me down. I have to admit I've already had some advice from various members while the intial build was in process.
former user, I get my plasticard sheets from Antenocitis Workshop or my local wargming shop (when he has them in). You're right it's not cheap. Dont forget Outpost sell some rather nifty generic frontages you can use. I'm about to order some bits from them:
http://www.outpostwargameservices.co.uk/Dewbakuk, I thought about guttering but I'll def be putting some on my next build.
gamer Mac, I've based it on some 3mm hardwood, it hasn't warped yet.
The boiler is a HO scale oil storage tank from Knightwing. Svennn put me onto the site and there's some nice goodies on there for industrial builds:
http://www.knightwing.co.uk/cgi-bin/commerce.cgiThanks again all.