I took a leap of faith before Christmas and bought the Chinese stove off Ebay that Rik posted as a suggestion. I took delivery of it today (having accidentally requested it be posted to my work address ;-)
I'm very pleased indeed. Here are some pictures. It fits inside a 10cm Zebra billy like it was designed to from the start. The lid fits snugly on top without being raised at all:
This is what it looks like when taken out of the Billy:
And unfolds like so:
The view from underneath:
Detail of the burner where the gas enters, showing the preheat pipe:
The valve and attachment for the gas cannister - the union with the pipe at both ends rotates to allow the cylinder to be used inverted in cold weather:
With the 10cm billy on top
loads of spare room up there:
And a very nice and very controllable flame:
After about 10 minutes of playing with this stove I would definitely recommend it. We'll see how it goes in use ;-)
Peter