Thanks for suggestions. The reason I was considering a set-up with the camera lens is that I was thinking of using a Pentax and the adapter I have got clamps onto the microscope eyepiece tube and has a 52 mm male filter thread at the rear. I have been looking for another type of adapter which does not need the camera lens. I found a nice cheap one from India for Nikon, have bid for this, the only Pentax one I could find was US$125 seond-hand, but I will keep on looking.
What am I trying to photograph? Anything interesting, probably at about 100 - 200x, i.e well beyond the range of macro bellows. I have several boxes of ready-made specimen slides, I shall make some of my own later. The microscope I have right now a simple student model by Meopta, it has a non-standard lens fitting, 3 lenses in a turret, but the optical quality seems quite good. I have taken quite a lot of photomicrographs in my time but never had to set a camera up from scratch!
Thanks once again and best regards,