Unvented hot water system

I had a system working well for seven years with fantastic power in all taps and showers.
Suddenly the bath takes twenty minutes to fill and the hot water flow slows down drastically when the ccld water is turned on. In the mixer tap the rate of flow is very slow whether it is hot or cold and no faster with both on. If a tap is on anywhere in the house the rest of the house has very little flow.
British Gas who give me my cover have been but cannot solve the problem despite replacing various valves. Any ideas?

Hi

Tell us more about the system type, what parts BG replaced. The lack of pressure to hot and cold could mean a blockage or main stop cock not fully open.

HTH

If nobody has been messing with stop cocks etc then it could be as simple as the line strainer blocked, if both hot and cold are affected then it sounds like you have a balanced supply so both are taken after the line strainer,PRV, etc this is correct installation praactice, as said before though what have BG replaced ?, has it been serviced as it should be, if not get it serviced by somebody who is qualified to do Unvented they shuld find the fault.

as above. ideally you should have a cold supply that comes directlyof the main-perhaps your kitchen sink or utility? is the flow and pressure significantly better on any of these?