Had a couple of goes with a USB stick and it really didn't seem to want to work, so I've put together a firewire DVD drive (old firewire hard disk casing with an old DVD Drive) and it booted OK and seems to be working so far, about ten minutes into a 30 minute install (yeah, right). Not exactly fast since the data is going through Firewire 400 ports at both ends, but hopefully I'll get there in the end.