Good list of XML Web Services?

I'm building an Affiliate marketing website which provides lists of quotes for credit cards, travel insurance, mortgages etc. I need to be able to link the list of credit card rates to a live rates so that when they update it won't be a big trial updating our website. I was thinking of using XML web services but I haven't found one which will give me the information I need. For example:

Barclays 3.9% APR credit card
Natwest 2.9% APR credit card

Does anyone know of a good web service (doesn't have to be free) which will do the job? Any alternative ideas are also welcome.

Many thanks in advance.