The problem is not the problem; the problem is your attitude to the problem - Captain Jack Sparrow
We decided....no, I decided to change the waterfall and The Man That Can did the graft.
As you can see it looks fine. It made a lovely sound and since it's fibreglass will last longer than the original plastic version. It will look lovely once it's naturalised.
I nipped out a little later to take some photos since I'd potted up some pond plants earlier in the day and needed to wait for the water to settle again. To my horror there was a strange sound coming from the pond and the pond was all but empty of water!
TMTC quickly came to the rescue and spent the next hour trying to fix the problem, which is that the water is leaking from the hose either at the connection point to the fall or somewhere along its length. I refilled the pond and until we can devote some time to it (at the weekend for instance) we have left the pump switched off.
A few plants including oxygenators and a waterlily have been added to the pool in the Yen Garden. No leakage issues here.