Johno, please keep the thread going rather than tell us after you've made an attempt at things we haven't discussed. There are some complications regarding valve lapping, checking the valve guides, and cleaning/measuring the piston, that could work out badly if you rely on guesswork. Meanwhile, though, some pictures of your piston/rings when you remove it, measurement of the ring gap for your old top compression ring, and a picture of your bore after you de-glaze it, would be useful for the archive.
