Ok last night I put each drive in turn and booted with the BIOS in RAID. It loaded everytime.
As I loaded each drive one after another, 1 and 2 loaded ok and showed up in the intel raid ctrl+I list. When I added the third drive (the one I thought was faulty at first but tested ok when I ran the WD tests) the RAID list shows disk 1, my 80gb SSD and the 2nd 500gb, the 3rd disk shows as a blank space where the S/N goes and 0.0GB as its size. I thought the drive was faulty and when I remove it and use the 1st, 2nd and 4th disks it still goes mad.
Got 4 160GB's to try when I get home.
Anyone else had anything like this? Might even try a slightly older version of the BIOS.