Many thanks guys,

Thanks for that JonS, nice link!

According to the diagnostic lights mentioned in the 2350 doc, "Memory modules are detected, but a memory failure has occurred.."

EDIT: I pulled the memory and got beeps! memory back in and no beeps, power supply stays on! Looks like a badly seated memory module was causing the problem. Now I'll put it all back together and see what other surprises it has in store for me! :-)

I did suspect the Bios battery might have failed, hence the question about some etherial connection between them but when that has happened in the past, I'm fairly sure that it still got as far as letting me get to the bios info... I'll have a better look later..

@James; could you apply mains power to your power supply and tell me if the fan spins up - (and stays spun up) without anything connected to it please? That might resolve another issue for me!

Thanks guys! looks like I might be in business!