Fitted a new MOBO Asrock 4 core sata 2, and Intel dual core 2200 processor.

Currently minimally fitted out with:
2 IDE H/disks,
DDR Memory
AGP VPU Rad9250 128adt

Boots, fans spin, disks spin, data activity, but no display, not even POST

Appears to boot successfully into windows, because when disk activity stops, you can do a CTR ALT DEL, ALT S, ENTER to shut it down. This is perfectully successful, and would indicate that, PSU, CPU, DISKS, MEMORY, and at least a part of MB functionality id OK.

PSU two tried including new one.
VDU works with another PC
graphic card works OK in another PC, also another AGP card tried, same result.
MB and processor new..

Very frustrating, can anyone think of anything, the only thing I can think of is faulty MOBO. Thoughts?

Have you tried another monitor?

Yep.
Two different monitors, three different leads, analogue and digital, all of which have been tested on another PC.

I have also established that it is indeed actually booting into windows, because I have managed to log in, and out, and repair a couple of USB drives that needed to see windows for proper shutdown, to be recognised on linux. That was done blind, but it did work.

I'm tempted to go buy a PCIe card with my last few shillings to test that slot out.

It will be a right royal pain in the botty to have to return the MOBO at this point

You might try a regular PCI video card... Does the motherboard have on-board video?

Took board back to shop. Shop tested it and found the AGP slot was duff. I just hope now, that it wasn't taken down by the card I have. Fingers crossed.