Ive cleaned the mobo, made sure nothing was shorting out, every connector, slot and removable chip and put everything back together and guess what - the machine will NOT boot at all.
I put in an A3640 changed the INT/EXT pins and still nothing. Im going to try and get an A3630 and try that as well to be sure.
Im really gutted as its only just come back from France from having the clock fixed :madashell:
Ive run out of options now so if anyone has a spare working 4000 mobo (pref a CR, REV D) they want to sell I'm interested, otherwise I may start to sell it all off and get a PS3.