It works!
However there seems to be a conflict with the WiFi card - if that's installed too, I get no boot, and all the front LEDs are lit.
Remove the WiFi card and it boots fine.
Likewise, install the WiFi card and remove the I/O card and it boots too.
I tried moving the jumpers on the WiFi card from 1 to 2, but that didn't help.
Any ideas please?