Thanks Alex and you're not wrong about the slop. After 4 - 5 hours of star gazing on Saturday I decided to see if in that time my collimation had moved and I was surprised to see the red dot just outside the donut. I gave the lazer a little wriggle and twist and it was dead centre again.
I was thinking of getting a Glatter but will give your mods a shot. I especially like the idea for tightening the lazer aperture.
As for putting a little black dot on my brand new secondary mirror.... I might have to build up some courage first.