Santander don't examine any credit applications manually, a computer credit scores you and then either rejects or accepts the offer. All applications can be appealled and then an underwriter (human being) will look at the case, usually they will send a message to the branch asking for more information, like credit card statements, bank statements, proof of address, they will then often overturn the decision. Also a declined application with one institution will leave a mark on your credit history and will make it MORE likely that other banks will decline you.
Having worked in banking, i cannot stress enough that going over your agreed limits does NOT help you get a bank account, or credit facilities with other banks/building societies.