@Franco B Cheers man
I ran into a show-stopper the other night: I have two spare motherboards (complete with cpu/ram) of differing age. One has AGP but no SATA, and the other has SATA but no AGP (only PCI-E). I wonder if you can see where this is going? I have one spare SATA drive, and my only s-video option (this is an old CRT TV remember) is an old AGP video card.
I was thinking of finding a cheap pci-e video card which is not hard, but I need it now, so that it can be ready for this weekend. My local electronics store didn't have any, but for not much more I found this neat little "PC to TV Converter". It's powered via USB, has a VGA in and s-video out. Perfect! So I got that hooked up last night and it works a treat!
So all I need to do now is finish wiring up the CP and setup MAME+frontend.
Will take some more photos tonight.