Well bugger me. I've found it.
When taking my car out for a charity meet at the Classic Car Show last weekend, I again noticed this strange noise, but this time as it was early in the morning and nothing was going to be about, when I heard this noise, I just stopped immediately and got out of the car to AGAIN try and investigate what might be causing it and to my surprise, I found that what had been apparently coming from the back of the car was actually caused by the outer edge of the front R/H tyre scraping against front fold on the aluminium plate below the door.
This just now requires a gentle? tap to move it back against the wheel arch.
How annoying but at least that is another problem solved