However I'm at a loss as to why I'm being told that there are updates available yet it's asking me to provide my credit card details to the App store just to get these updates.
One of the best things about the Apple App Store is that you
don't have to permanently save your credit card to your profile.
The only time I've heard of a situation similar to yours is when someone didn't have an iTunes account before. I think the first time you set one up it might ask for a credit card number, but you can always revert back to the "none" setting.
Infact, my profile spends most of its time in the configuration shown below and I can still download all App updates without issue, and certainly without needing to input a credit card number.
