An update. Well the second Mobo arrived and I have the same symptoms. I am now really puzzled. All I have hooked up is a) the CPU installed with thermal paste onto the stock cooler, b) the CPU 4 pin connector, c) the 24 pin ATX connector (that is in two parts - a 4 & 20 pin connector, and d) the CPU fan to the mobo pin. Neither CPU nor PSU fan spins up. Mobo power LED is on. I have an email into ASUS tech support.
PSU - Cooler Master Extreme power plus 500W
Mobo ASUS m4A88T0m LE
CPU - AMD Phenom X4 945 (which works in another PC).
Any suggestions welcome and greatly appreciated.