@accio-brain

The forum has a search option !

Have a look here :
https://retropie.org.uk/forum/topic/32069/retropie-wont-boot-up-start4-elf-not-compatible

@mitu Finally got it working ok with your help (THANK YOU), full upgrade using Putty worked although my laptop crashed and corrupted the SD card at around 80% of update and had to reflash it and start all over again.

But copying the two files across, then updating via putty worked in short.

Thanks,
Tom