We made it! I fired until the cone tip pointed horizontally- 995 degrees on the pyrometer.
So it looks as if I've got bisque firing sorted. One more bisque, for which I need to do a little making, then it is onto the first glaze firing in this kiln.
The cone in the background is one from the first firing- so I think we can say that cones do measure heatwork not temperature entirely. However it will be useful to put them in different corners of the kiln in subsequent bisque firings just as checks. (and saving the unfired cones for the front)
The new jug shape is still looking good!