Weird plumbing problem - any advice?

[Wimpole]

Any plumbers or homeowners out there have experience with this one? I have a 2 bed Victorian flat with a low water pressure/flow problem that has just arisen in the past year or so. Details:

- Flow is low at the kitchen tap for cold (and before combi bolier circuit is fed) where mains water enters. When my plumber measured pressure at this point (stopcock) it's 5MB which is good. However when flow is measured at this point it is low and below normal.

- When pressure and flow is measured on the street at meter it is good.

- We have shut off supply on street and kitchen stopcock and measured with gauge to test for leaks between street and point of entry to the flat. There are none.

- The flat above and below (GF) have no such issues and are fed via diff meters but from the same street main.

- the flow at kitchen tap by stopcock seems to vary from terrible to almost acceptable.

- the piping connecting my stopcock to the street is under a concrete path and communal flooring in the flat hall.

My plumber can't work out what could be causing the low flow rate. The mains pipes have not been tampered with, the meter at street and stopcock is full switched on and it was great for 5 years or so when I lived there.

It suggests some kind of blockage reducing flow rate? Any one come across this and have an answer or could advise next steps?

Many thanks....

Wimpole

[malumbu]

Had a gate valve once where the mechanism had dropped, so it appeared open but flow was severely restricted.

When you say stopcock this is at the street, or in your house? That's all that I can think of but a plumber would have stopped that. There are lots of self help type websits and other sources of advice.

https://www.thameswater.co.uk/Help-and-Advice/No-Water-or-low-pressure/What-to-do

[Wimpole]

The stopcock is at point of entry into my flat. The supply can also be switched off in the street meter under the pavement. The meter is newish but I suppose I could get Thames Water out to check...it costs about ?150 though and my plumber is convinced problem is not with them.