Thanks renormalised!
As I said, I'm certainly no LRGB expert
When doing the blue channel I noticed it was poor and just
assumed that Cent A 'just don't have a lot of blue in it'
When it came to the LRGB combine, I realised that I needed to
disable back the Red and Green to get the Blue to contribute
to the image. Sorry for the feeble , non scientific,
cave man descriptions here
I tweaked them until they looked right and didnt destroy the Lum detail
then clicked apply.
Hardly a good routine eh.....
I wish I could somehow upload the 4x LRGB FITs files and let people
show me how it's done...but they are 3.5M each!
Thanks so much for the advice,
Steve