As we're travelling, shipping wasn't an option. As the unit is a least 5 years old, I decided to open it up and see where it was leaking. There is a black valve unit attached to the back of the circuit board with 3 plastic hoses plugged in to it.
It was leaking at one of the fittings, which you cannot take apart. If you held in position it would stop leaking. There appeared to be nothing we could do to stop it leaking short of getting the silicone out.
I gave it a gentle push into the black "box" and it went in a few mm's. Leak stopped. I put it back together and it is working so far for the last two trips we have made.
At least I know how to take it apart...