If I decide to clean/overhaul the carbs which have never been done in the 15+yrs I've owned it
should I just

a. strip and clean (I have an ultrasonic cleaner)

b. strip and clean and replace all o rings/seals/ diaphragms/ pipes etc as a matter of course
(this is what I usually do with most jobs so I don't have to go in at a later date especially now as I no longer have use of a well lit garage)


any advice welcome

If the bike isn't your only transport open the carbs up, clean them up and see what you need.
The diaphragms may be ok, but you may need new needles so the money you save not buying diaphragms that you don't/May not need can go towards something else