I am after some 40mm ID silicon hose to attach bike carbs to a manifold. It does, of course, need to be petrol proof. Where can I get a short length to cut to my requirements.

FASTdan on this site:

http://www.danstengineering.co.uk/

Viper performance is one option

Linky

https://danstengineering.co.uk/index.php?route=product/product&product_id=182&search=Silicone

Try http://www.allensperformance.co.uk