The valve just came from Ebay - no name or part number on it:

http://www.ebay.co.uk/itm/151836051580

Everything else seems to check out okay now. It's just as soon as we connect the idle control valve up it starts to run erratic.

Tried from cold this morning without the valve and it started up fine, albeit running sluggish around 600-800rpm as it didn't have any assistance from the valve.

I can understand now why so many people leave them disconnected!