I've allways found this company helpful. Used to be some interesting articles and tips on rebuilding on their website. Don't know what's on there now.

I even bought spare parts from them for my Cosworth T5, even though it's a US based company they actually had Cosworth specific parts for the T5 at favourable prices. Most of the parts needed when repairing a T5 would probably be identical with a rebuild kit for the US Mustang T5 kit. I needed the input shaft with the splines to fit the Cosworth clutch (the Mustang has a different input shaft). They had the Cosworth input shaft in stock!

http://www.5speeds.com/