On my Vaillant, CH is fine, HW not working, called the local plumber,
he said its diverter, £150 parts + 70 fitting. I googled for it, its
about £90.

Is it easy to fit, where do I get the manual from, can I do it my self,
is it advisable.

Could it be any part within the diverter, or do I have to replace the
whole thing.

can any one help please.

Sukhi