Yep, as Peter said, it went very well!
Prior to making the adjustment, the poor Cat gave a very dodgey image. Low power stars showed a 'tail' and high power was impossible to use.
Post adjustment, holy cow! I first secured the secondary and then checked the collimation - Unless I was doing imaging with this C8, I really wouldn't attempt to collimate any more. We fluked a position on securing the secondary that gave a collimation result within a bee's d..k of perfect.
The Moon was extraoridanary, and M42 was brilliant for light polluted skies and a first quarter Moon to contend with, & with pin sharp stars at high magnification.
The process went smoothly. All the marking to look out for were there. It paid big time to ask and read the posted links!!!!
Many thanks everyone for your considered advice,
.