Hi John,
I don't know if I have the manual you are looking for as it has a "H" after the other letters & numbers that you wrote!
I have an "Instructions for Installation & Servicing" manual for:
Vaillant VCW GB 221 H
COMBIcompact
Also written on the booklet is:
GC-NO. 4704414
Wall Hung combined appliance for heating & domestic hot water.
Natural draught balanced flue type.
Is it the one you are looking for?
Vanessa, January 2006