Again Natwest, again an account management centre rather than a branch. That is there are probably dozens of branches covered by the processing centre.
What are you trying to check out? For most purposes you don't really need to quote the branch even if the form asks for it.
http://www.postcodeanywhere.co.uk/products/bank_validator/demos.aspx may help - if the postcode doesn't match the place, then it's a processing centre.