Thanks Astro,
I just happened to find a nice calculator with recommendations on exit pupil and magnification -
http://www.stargazing.net/naa/scopemath.htm
Adding more maths
but I have read on other posts people suggesting EP's based on exit pupil more so than actual magnification.
With that in mind, in my 10" F4.7 Dob:
ES 6.7mm 82d - exit pupil 1.4mm
ES 11mm 82d - exit pupil 2.3mm
ES 18mm 82d - exit pupil 3.8mm
I think those might do to start with ... VTI in Oz don't have other good sizes in stock atm.
The search and research continues ...