In English, we don't use a different pronoun in order to be polite. For example, in French, you say "vous" instead of "tu" when you are speaking to someone you don't know or someone who is older, your boss etc... There are other languages where this happens too like Afrikaans and Dutch.
So, what do we use? Well, we use modals like could, would etc... as in the polite forms you mentioned above and we also use the simple past tense even when the action is going on right now. For example, you are opening up a bank account and the teller asks you "what was your name?". This doesn't mean that she is asking you what your name was in a former life! It just means she is being polite.
Have a look at these links I found a while back:
Imperatives VS Polite Requests Modals for Polite Expressions which is a board game for polite language using embedded questions (look for it in the list under the pre-intermediate level ESL board games).