How do i replace idle speed control valve on 1997 escort?

Hi

I need help replacing the idle speed control vale on my ford escort, it's a 1.6 zetec on a P reg. The first hurdle though is finding out the part number as there are two apparently and Ford have been useless with the information they have provided me. So if anyone can tell me where the part is located within the engine
bay I should be able to get the part number and get a replacement from a breakers.

Any help would be greatly appreciated, many thanks, Barry