One question though, boiler pressure is showing 2.5 bar now. Was showing f75 fault pump/water shortage which I have seen before but manually turning the pressure back up using valves below the boiler resolves this. Is this a normal or safe pressure for the combi boiler (valliant)? I'm assuming its all safe now (in terms of flooding and leaks) once the TRV and valves are securely fitted on? Definitely taught me a lesson and got me more cautious and nervous too.