Hi!
We too have had water pressure drop over the past few weeks, down Garthorne Road. I have yet to check the stop cock in the street which just supplies our house, to see whether it is fully open and I do not have the tools to do this.
The water company has been checking the area for leaks recently. This involves them going round and listening via a long pole to the water pipe in the street to see if they can hear any flow of water. They usually do this in the middle of the night, when no-one is using water. We had our stop cock on the pavement sprayed with blue paint as a result a few months back and (after checking the validity of the request direct with Thames Water) had a sub-contractor (PN Daly) come and check it out. He could find absolutely no leaks whatsoever but that did not stop another note being dropped through my door asking to contact Thames Water about a potential leak. I ignored that notice, so perhaps they have punished me by half closing off the stop cock to my house!