Unless the credit or debit card's billing address is in Britain then no. There are cards that you can buy and top-up online i think, so if you're really intent on purchasing stuff from the store, this will be the only way to do it.
The downloaded content is isn't region-locked but you still need a credit card linked with the country that your buying from to purchase the content.

Patches for games are not downloaded through the PS Store. Whether you have the PS Store or not, shouldn't affect whether you get patches or not.