Well, just an update on the cable issue. Apple store in Regent St London changed the cable for me. I made a specific request for them to please keep the cable for me so I could compare it. They charged me for the 'repair' given the original one was working with the HDD.
So, two trips to the late running chaotic genius bar, four hours spent and a new cable installed, but surprise surprise - despite the written request being on the work slip - they binned the original cable.
So, as far as I can tell there is no obvious change to the cable - sheilding can often be seen and it is certainly no thicker than the original - so I think I just have another cable as opposed to a different one.
Performance is as expected, still cannot boot from the Crucial M4 SSD if it is on that cable.
I also asked Apple Genius if they could install an apple SSD for me, no they couldn't
Could they reccomend an SSD for this model to me, no they couldn't
Could they tell me what drive would have gone into this mac if it had been built as an SSD model - no they couldn't.
Genius! Basically they can only support the exact config as purchased.
Next steps.... try a vertex III 240 GB, the 480 is a mad price, and try connecting using an OCW data doubler (just purchased on eBay as you can't buy in the UK) to see if that can even see the drive at SATA 2 speed (given that it works at SATA 2 speed in my MacPro)
Send the Crucial SSD back to Micron UK (yes they are the same company) for a swap - given that it still says 'guaranteed-compatible' on their site, see if a newer drive with the 0002 firmware pre-installed is any better.
Will let you know if any of that works.
Stephen