"I'd check things methodically from your stopcock onwards. Start by measuring the static pressure / flow and dynamic pressure / flow from the first outlet after your stopcock. Ideally this would be at least a 22mm outlet. This will tell you if your incoming supply is, indeed, up to the job. If you can find out which showers you have, you'll be able to see what kind of flow you require (probably 15 l/min or more).
Next would be the same measurements AFTER your PRV multi-bloc. There is a strainer in there too, but given a new bloc was fitted, it's unlikely that would be clogged up (but possible).
Assuming both of the above are ok, move onto the first cold and hot outlets and test those independently. Try bath taps and sink taps to rule out individual taps being at fault. Take heads off of showers and measure the flow directly from the arms. You get the picture -- it's time consuming, but eventually you'll narrow down where the problem is. Something I think your G3 plumbers should have ideally done rather than just randomly changing parts in the hope it fixes things"
WORDS OF WISDON: And what i would of hoped for- had i known /asked on here, although really i should not have to. As you say and i concur they where all licensed . 2 x are on the megaflo recommend installers list!
UPDATE:
Great news. I have changed the 2.1 bar for a 3 bar and standing pressure is 3.0 after the PRV and on the megaflo 3.0 also.
I assume that's as good as it gets?
I have had the main big rain fall shower running, 2 x sink taps and flushed a toilet and very little drop in flow too.
All in all as I read the thread back it sounds like a panic!, I was just a my wits end.
It all started with low pressure and me insisting I wanted the 3 bar PRV changing of which 2 plumbers insisted it would not be the issue.
Plumber One: recharged the megaflo, off which I now know i can do myself.
Plumber Two: Fitted 2 valves and insisted it was united utilities:
So we started with 1.5 bar and had 3 plumbers out, we have ended up with 2 pressure gauges fitted (on the incoming upstairs and one on the megaflo) so thats fair enough as at least now i know what we are getting (although i can not help going upon stairs every now and then and checking them)
Plumber Three: Fitted a 2.1 bar PRV and made it even worse, I am now suspicious of this as he did say he would be back to further investigate on a day rate. I looked at the PRV when he had left and noticed the part of the plastic washer - label on the PRV where it says 2.1 quite obviously had been turned out of sight, so it was not able to be read, it was only when i turned the ring round by accident i saw it was 2.1 Bar.
I have had a friend who to be honest is not a qualified plumber but works on houses as a full time maintenance person swap the 2.1 bar cartridge for the 3.0 bar one, it was a like for like fit.
He took the old original 3.0 bar PRV apart and it was failing apart inside (7-8 years old) so.....
Bingo! As i suspected all we really needed and what i had requested, a replacement 3.0 bar PRV (A new cartridge may have even been ok) it was my call to replace the valve though.
So the moral of the thread:
*Don't panic like i did and get stressed about it.
*Get a plumber you can trust
*Even better a plumber recommended.
*Use a forum such as this "and be honest" don't be embarrassed to ask even if you think you may be right "Ask the professionals"
*Listen and it will all work out
Finally update any posts you start, no matter what the subject as there is nothing worse then finding one thats exactly the issue you have, reading it all to find the original poster leaches all the knowledge and is selfish enough not to share the solution for those to benefit from.
Thanks to all on the forum for reading, helping and not calling me stupid!
Respect.