So I checked, and re-checked, every transistor I could lay my hands on. Nothing was suitable for 10W. Nor does it appear anything can be purchased that might be suitable that has not been tried.
Several transistors in plastic encased TO220's worked fine at a few watts but couldn't cope beyond that.
From here I have stopped looking for a general purpose transistor for a single-ended amplifier.
A board is being layed out with parallel SOT89's. Since 2 of these in parallel class A could easily deliver 1W continuously it is reasonable to expect that 10 of them, operated class AB in push-pull, could deliver 10W.
Something to be put to the test in the near future.
73's
Richard