Better news tonight. I'm a tad more optimistic. The level has held over the last 24 hours, and the newspaper underneath only has two small specs of damp. The orange triangle is set halfway between Min & Max, and I strongly recommend that you mark your expansion tank to show a specific marker against which to measure. This is lens repair tape from Halfords.
This photo shows just how tight the access is to that hose when the washer bottle is in place.
Looking down from above - which shows the thermostat housing hard up against the bulkhead:
And this photo is taken from underneath looking vertically upwards. That's the water pump pulley and the visible Jubilee clip is the lower one on the tricky hose. The metal pipe curving to the left is the one which goes under the nearside exhaust manifold, and it was from this pipe that my water drips first started.
