Thanks for your response, David. As you spotted, I'm in the UK!

I can't see how the front centre logo ring comes off - there are no visible set screws. All the screws seem to be on the back face of the lens, where it contacts the body of the camera.

I've taken apart an Industar-26m for lubrication before and that was a breeze. Gotta love that Soviet simplicity! This Mamiya sample seems to be a bit trickier. I took off the inner rear ring (with the electric contacts) and that was easy enough, but all of the screws on the outer ring were stuck and I couldn't get them to move. Not having a great deal of success!