Call XML Data Feed then pre-populate an OxyClassifieds form

I have an OxyClassifieds site which is used to advertise cars. I would like the ability for a user to type in their car registration number which would then automatically fill out the advert form with their car make, model and some other information based on the cars registration number. I use a company which can supply an XML data feed with the data based on the cars registration number. So I would require a form that calls their server for the XML file from the cars registration number - then pre populates the advert form in Oxy Classifieds. Required Features • A form that requests the users registration number - when the user clicks send it would request an XML file by using this URL [login to view URL] - the REGNUMBERGOESHERE would need to be replaced by the users registration number. • The form would need to keep the username=MYUSERNAME and key= MYKEY arguments of the above url hidden (as these will feature my personal username and key that I don't want people to be able to see) - possibly by using SSL requests or another method. • The XML file that is provided by the registration number company would then need to pre-populate the OxyClassifieds advert form - I attach some example XML files, also below are the names of the fields in OxyClassifieds and next to each one is the piece of the XML file that I would like to be pre-populated into it. Title = just the year from first_registered, smmt_marque, smmt_range and colour Make = smmt_marque Model = smmt_range Year = just the year from first_registered Transmission = smmt_transmission Fuel Type = smmt_fuel_type Colour = colour Body Type = smmt_body_style Engine Size = smmt_engine_capacity • If items of data aren't available from the registration database company I am using then I would like the system to leave those items blank (so the customer can fill them in). • This system would need to be tested and develped remotely (not on the live site) as the site currently is in use.