Yep - Cheers for the response Zorlon

I got it sorted and thought I'd better get back here.

What you have mentioned is what I had done - needed the right BIOS and then just tried different games.

For anyone else who might come across this thread owning an RPi, the es_systems.cfg file at /home/pi/.emulationstation/ also needs to be edited for best results. That is there is way more chance of running games using piFBA so comment out the line starting with COMMAND = relating to the currently used neo geo emulator and uncomment the line straight underneath it relating to piFBA which starts with something along the lines of # Alternatively use COMMAND = blah blah/blah/..../........... piFBA

Hope this may be of assistance to someone if they are doing a RetroPie project.