Completely Front End with heavy DB usage

Hi I am starting a new venture and I am looking for a web designer with DB integration skills. Briefly the role will involve the setting up of secure interfaces on the site so that information from various sources can be automatically integrated into the site, an example given below. A dynamic front-end website, incorporating heavy DB usage will be needed to support this functionality. This is not the project, but this example should give you an idea of what is needed. PLEASE NOTE THIS IS NOT GOING TO BE A CAR SITE!!! Let us say (for example) the project is going to be providing information on all the cars in the UK for sale.. There are probably 50 or so sites in the UK selling cars. The site will need to do two most important things. 1, be able to accept feeds from the busiest sites that are out there, i.e. [login to view URL], [login to view URL], [login to view URL], carsource.co.uk. These feeds will need to be entirely automatic, so that the data we receive from these sites is integrated into our site seamlessly, automatically, and as instantaneous as possible. These feeds will be sent to us, and will also need to be polled from other sources. I.e scanning autotrader, once an hour and retrieving all new listings. 2, we will also need a facility, whereby via a secure web-page, registered users can log in, and enter the details of the car they are selling using pre-defined fields. The front end of the website will need to be as user-friendly as possible. The end-user will need to be able to search on car type, location, price etc…. PLEASE NOTE THIS IS NOT GOING TO BE A CAR SITE!!! The site must also be able to process online payments, via a method of your choice, such as worldpay, paypal, etc…. Further details can be obtained on request. Please note. Please do not send me dozens of URL’s for sites you have done. I only need to know that you have been involved with a site that can accept interfaces to other sources of information, either by actively polling them, or by receiving feeds from them. I think the secure posting should be a doddle for any decent designer. If you have not had this type of experience, but think you could do it. I will provide you with more info, and a sample of data to show me what you can do with it. Sorry for the long spec, but it is important that you can do this before you apply. Thanks jm@[login to view URL]