SOLVED!
After a couple of drinks last night, and a bit of logical thinking, I decided to take the Phenom II X2 550 BE out of my pc and put it back on my old GA-M57SLI-S4 motherboard as that was the only thing that had changed from the X2 6000+ cpu I had been trying to get to work.
BINGO....It started up and I got into the bios with no troubles. So after a couple more drinks I thought well maybe it didn't work because at the time the Phenom was installed, I had put a beta bios on from gigabyte tech support (FHO) to cure the slow boot problem with my ATI HD5770 graphics card and the inability to overclock the 550 black edition cpu. I then put the bios FD (which was the first bios to support the x2 6000+) onto a usb stick and flashed it to the motherboard. I then shut down the mobo and swapped out the phenom for the older cpu.
Switched it back on and.........................1 short beep and a press of the "Del" key and I'm into the bios again. Problem sorted!

On a cautionary note, don't drink and fix pcs
