I could go and buy another mb/cpu but I'm thinking instead about using a PCI extension card with USB outputs. The question is though, will this still route through the mb USB circuits. For about £10-15 unit cost I suppose it's woth a punt.
No, it is independent of the physical USB wiring in the mobo.
Providing of course that you don't connect the internal USB output on the PCI card (if present) to the case USB ports!!
SD