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I think I might have solved it! After careful study of the view through the cap, and looking at pics on the intertube I came to the conclusion that the secondary was not centered under the focuser. There was more gap on the right than on the left. So I undid the centre screw and moved the secondary down the tube by about 4-5mm. Using a paper baffle to block the primary reflection and a piece of paper behind the secondary I got a perfect circle, centered under the focus tube with all six clips clearly in view. Removed the paper baffle blocking the primary reflection and the donut was off centre. I put in the laser and to my astonishment the beam was only just outside the donut, right on the edge. So a minor tweak of the secondary was all it took to put the beam on centre. Primary was well off the return bullseye so I adjusted that, then the cap went back on to find that everything looked as it should with donut reflection bang on centre. Woo! No idea how it could possibly have got so far out of wack. Meanwhile, I've bought a Cheshire on eBay, and roll on tonight's dark for a look see. :-)
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