noisy Ideal mini combi boiler

Hello to all

Hope someone out there can give me some sound advice prior to calling a plumber. I have an Ideal mini combi boiler which is approx. 3 years old now. Over the last couple of days when filling the bath with hot water, the boiler makes a screeching/screaming sound. The noise also occurs with the hot water feed to the washing machine when in use, but not when I run the hot water tap to the sink?

Any advice would be much appreciated!

Cheers

It's an O ring deep inside the water valve parts. Quite a lot of work for a noise which will probably change/go away/come back if you fix it once