Problem solved!!
Forget needing a 512Mb model, forget needing an aproved PSU (some of the responses I had from their sites)...
2 ran quiet (PN 102-B34003-
00-AT), but on some games like BF2142 they were running at 93 degrees and suffering lags and corruption unless I dragged down the screen resolution below what I had on my previous 8600GTS
The other one ran noisy (PN 102-B34003-
01-AT), which annoyed me initially but had no lag problems with all settings on high.
I used CPU-Z to get the temprature & fan readings and WinATIflash to take the BIOS from the 01 model to the 00 model and guess what all 3 cards now work flawlessly (although I have fan noise when game playing)!
Even though the BIOS versions look to have the same numbers and file size there has obviously been an alteration made regarding fan speeds. I think I read somwhere there was a typo was mad ein the BIOS where a comma had been used instead of a full stop. I wonder how many GPUs they burned?
00 ran at 93 degrees, 01 runs at 73 degrees a whole 20 degrees cooler!
DinoHunter (still no nVidia compo voucher!), CPU/GPU Benchmark, DarkFish Encryption DLL, War MMOG (WIP), 3D Model Viewer