There's no condensation or water leakage anywhere. The boiler is located in the kitchen over the counter and there has never been an accumulation or puddle of water at any time.
Nothing there either, dry and no indication of there being any form of leak.
For your information, I refilled the system this morning at 0830, and ran the system to reheat the water and radiators, which has now depressurised to 0 bar. There is no leak of water or condensation anywhere in the house, nor outside under the flue.
Should the FW valve be open fully and constantly, or is it left shut?
I've had a look and there is no PRV discharge pipe, and is only the flue outside. Whether this would be in the fabric on the wall and venting underground, I don't know as this is a rental property.
I shut the system and the valves, refilled the boiler, vented and re-flashed up the boiler. The pressure dropped to 1 bar, so I repeated to 2 bar and re-flashed up the boiler. The pressure has now climbed to 3.5 bar, so I've returned the system to timer and will see if it drops.