Hi David, thanks (once again) for your responses.
I was making life difficult for myself in the belief that I needed a reference star close in proximity AND in spectrum to the intended target. (Indeed I’d noticed a better fit when I did that).
I’ll relax that spectrum requirement (and the time it takes to find a suitable ref star!).
(That does indeed solve the issue of ‘what ref star do I choose for a binary of differing spectral components?’. Doh!).
It looks like being fine up here tonight so I’ll chase a few more Be and ARAS symbiotics. I received a good response and a few ‘pointers’ from Francios T on submission of my first spectrum to him and I’m keen to try a few more.