Hello all,
the aforementioned toilet is now installed and is leaking! It is a BIIO cistern (actually a B&Q 'Toilet to go' which is a close-coupled cistern) which leaks into the pan so it's not disastrous. It is not overflowing through the top of the overflow pipe as that is several cm above the water level. My best guess is that the flush valve has not seated with the seal washer and/or lock nut correctly and is leaking that way.
Should I remove the cistern and tighten the valve? (I think I have tendency to under-tighten such things, due to a fear of over-tightening!) The cistern does not appear to be leaking externally at all. The area around where the cistern and pan meet are dry, as is the floor.
Is there anything else I should check for? Does anyone know of an online diagram explaining precisely how these flush valves work? Suffice it say that the enclosed documentation is of little help.
TIA as ever, Pete