High water pressure all of a sudden??

There is a difference between flow and pressure, turning the stopcock down wont reduce the pressure that much unless you turn almost off which is a sticky plaster fix.
To effectively change the pressure correctly it has to be with a PRV (pressure reducing valve).

In compressed air applications, you use a flow regulator to slow down the speed of the air but maintain full pressure, if you wanna reduce pressure it has to be with a pressure reducing regulator / valve.

Right, can't find the blasted thing. What she found were those electrical safety clips attached to the pipes.

The pipes go down behind the level of the cabinets and seem to disappear behind the wall (I look down and found two perfectly good sponges and dustcloths which I don't really want to try and retrieve lest I get spidered) so maybe it's outside on the side behind all the vegetation and flowerpots I've never bothered examining closely (the lawn is my priority, the previous owners seemingly had never cut it so I am nursing it back to health)

HOWEVER it doesn't seem as pressurey today... the sinks and shower both don't seem to have the same blast of water trying to get in. Also, a letter from Dwr Cymru informed us that we're switch our water source from one reservoir to another which *might* explain something. Odd the woman on the phone didn't mention it.