Thks blckhaze,
yes the new Motherboard did not want to start, all fans spun once then dead, I have tested the new MB with the Radeon Graphics and it works fine. I am guessing that the new P5KPL Mother Board has some sort of sensor that detected a problem and shut everything down. I am not going to bother sending the new MB back, all cables still in bags, untouched etc. but you really do need a spare PC. (As two days without one, showed me. Had to phone a friend and get him to order the new MB, life is sooo much simpler with the internet and cheaper too
My backup PC (a laptop) is up the spout and I think needs a CMOS reset but that is for another thread.
The old Asus GPU was definately the problem as I did the old disconnect/remove to see what starts. (Removed all PCI cards, disconnected all Hard drives/CD's, started PC with CPU got beeps, switched off, added back memory etc until I got to graphics card and one spin of fans (2 chassis and CPU fan) then dead with no beeps, no flashing MB lights/just normal green MB power light.
In terms of air flow I think the hot weather last week must have pushed the GPU over the edge, although the card had it's own fan (Asus 9500GT 1GB DDR2 DVI VGA HDMI PCI-E) and its PCI-E slot is situated near the two chassis fans. I noticed an "extra connector" on the MB for a power supply fan which is not in use as my power supply's fan is intergrated in the PSU. I will spec out a oversized side fan as I have air-intakes there. Otherwise it will have to be a PCI slot fan or below the HD's.
Thanks everyone for your help.