Well, a decision has been made, though not what I imagined when starting this thread. I've just ordered a 12mm Nagler type 4. I've decided to go for a premium 8mm down the track, but in the meantime my 8mm ED will suffice. The 12mm will give me 225x with 0.36* tfov, so should get a lot of use.
Thanks to everyone offering advice
.
Stephen