Thanks for you comment, however I have insurance policy which covers the boiler. The fact is the engineer has not dealt with the expansion vessel pressure correctly, which has been stated on this post by other members and I totally appreciate their input. And refusing to replace a PRV which was leaking at 2 bar pressure is beyond my belief even with the little knowledge I know re boilers. The engineer who came out on Saturday is due to come back, so I will ask him kindly to 'properly' check expansion vessel pressure and pipe connected to it. From what has been stated so far the fault lies there. Also, the old vessel I still have in garage, still had pressure in it (less than 0.1bar though) as pressing on valve let air out. I have repressurized to 1bar and it still has same pressure in it 2 days later, so it originally 'probably' only needed to be pumped up. If only I knew then what I know now.
Also if I don't try & use CH, pressure stays the same at 1 bar, so this eliminates other possibilities and I always disconnect filling loop.
Also if I don't try & use CH, pressure stays the same at 1 bar, so this eliminates other possibilities and I always disconnect filling loop.