Well what can I say.
powered up PC this morning, and nothing apart from a smell of burning. Quickly switched off mains, opened up machine and no visible signs of damage. Power button did nothing apart from light two LED's in front of the RAM. Move power supply from another PC. Still nothing - same LEDs light, but everything dead. Decide Mobo has died and take it back to supplier who has none in stock, but swaps out to a UD5R with extra payment.
Put Mobo in PC, processor and Ram, back to old PSU, same result, dead but two LED's lit. Try previously used alternative PSU and still nothing.
I'm now extremely depressed.
Even more depressed after looking at price of new i7 processors.
Put swapped PSU back into its PC and now that won't start. Mobo power light comes on but PC dead. Decide to check PSU outside PC using short between green wire and ground with a fan as load - nothing on both PSU's
OK. Swap PSU out of yet another PC and it bursts into life!!!!!!
Off to supplier for £80's worth of PSU's. Install in two original PC's and we're back in the land of the living and I'm a happy bunny at last.
So the Mobo had blown and taken out two supplies with it