Well... if anyone searches for this issue and finds that my answers helps them they should also be banned

This was a new setup so when it came to the options/config screen I should have been hitting the button with the dots in it to set the MAME executable but I wasn't. I was hitting the "Config button" . That gave me the "no mame ini file found! create a standard mame ini (.ini)?". So I was hitting "yes" to that which was when I was getting the "attempt to create /.ini file failed".
So, having realised I've not been paying attention and pressing the wrong button, I hit the 3 dots button to set the path, and then the same for the ROM path, it's all working.
Somehow I figured that the error message about creating the .ini file was related to permissions. I must have spent 3 hours messing with permissions, reinstalling the OS, changing partions, trying older versions of Mala.
What a muppet.
Anyway - alls well that ends well
