UPDATE!!!
Finally got it to work!!! For those with a similar issue. I deleted the retroarch config files, then cleared the controllers via emulation station. next I reinstalled Retroarch, and rebooted, meaning Emulation station allowed me to remap the controllers.
Despite ES showing my controllers and assigning them to the Retroarch_joypads folder as DragonRise Generic USB, Retroarch had it as DragonRise N64.
So I just copied the file from udev folder, into the Retroarch_joypads folder, and deleted the other one.
Next I went into Retroarch itself via the setup menu, and selected the Control tab in Setting. The new version gives some nice new options, such as Quit Retroarch combo (I think) and Toggle menu, which I set to "Hold Start for 2 seconds".
There is also a menu option further down the list that i set to a spare button just in case.
I then copied the retroarch config file from the all folder into the arcade folder, replacing the one in there.
I then launched pacman, held down Start for 2 seconds, with great relief I got up the menu, carried out what @lostless said, and it works a treat!!
Now on to the next load of 4-way games!!

Okay. I was able to fix this by re-installing RetroArch. This doesn't explain what went wrong the first time, but I'm glad I get to enjoy this wonderful emulator now.

Feel free to delete this thread.

Keep up the good work!

Retried using Android mode on the controllers instead of Switch mode and everything seems to work fine. I'm going to go with that. Thanks!

@flamingflareon Are you able to save from the RGUI ? You can save pressing Select+X, then using Save State. Does this work ? If it does not, then take a moment and give more details about your system - https://retropie.org.uk/forum/topic/3/read-this-first

@ben-almonte Update to retropie 4.3. Reconfigure your controller. The last button to configure is the hotkey, so you can assign that to something other than select.

solved by OS reinstall, thanks guys.

@gusrod1580 Yes but earlier in the file you are assigning 8 to select and enable hot key as well as exit emulator. So you will get no functionality even if those last lines are removed.