PHP (& Smarty / Flynax) Dev needed to add vehicle registration search to our w/site

Need somebody who can modify our classified auto's site to add a vehicle registration lookup facility which would auto-populate the form fields when our customer is listing a car to sell. We've looked into online vehicle data providers and found cdl which use a http GET request to return an xml file so would need somebody to be able to get the vehicle data into the form fields. Website is PHP but built with Smarty.

Website: ukautotrade.co.uk
If you click 'sell a car' at the moment you have to choose car make/model etc - would want that to be automatic from the vehicle registration search

Which is in itself built with the Smarty PHP template engine:
http://www.smarty.net/