Hi, this is Worcester, Bosch Group
We have a boiler repressuraisation section on our website which should be able to help you. Link is:
http://www.worcester-bosch.co.uk/homeowner/products/faqs/boiler-repressurisation/how-do-i-use-an-external-filling-loop
Alternatively our technical helpline advisors are available on 0844 892 3366
Worcester, Bosch Group, August 2010