high pressure in circuit

[AlanRus]

I have a Worcester Bosch Greenstar CDi37, and the pressure is just over 3 bar. The PRV is open and dripping continually - not a huge surprise what happened was that I noticed that the system pressure had gone a little low (to about 0.7 bar) and I cracked open the circuit fill valve... the pressure rose a little, I closed the valve, and the pressure still rose!! I was pretty happy that it seemed to top out at just over 3, until I went outside and saw that there's water pretty steadily dripping out of the PRV. And now theres a repetitive noise in the system. Air maybe? So I've called the installer, because now its beyond a simple problem I think... however its Saturday, cold today, and the noise it bugging us! i'm thinking to drop the pressure in the system to bleed the rads, so off I went, turned off the boiler, then did the lot. No air in any, got water out of all - a few drips. No move on the pressure gague on the boiler at all. Then I took about a litre of water out of one rad. And stopped. So my question is : after draining out how much water should I see the pressure gauge move? And followup q: based on the above description should I leave well enough alone!
Help much appreciated. Cheers, Alan

 

[greemyamochop]

Try draining some from with a hose on the radiator circuit, shouldnt need much to drop pressure but make sure the filling loop is 100% off and youll need to bleed rads after