If you use the conditional, that will sound more polite, just as in English (e.g. "I would like to XXX" and not "I want to XXX", "Could you please XXX?" and not "Can you please XXX?"). I wouldn't try to be self-effacing or "humble", which is generally viewed as being polite in the UK. It's more likely to seem odd than anything else. It's better to be pleasant and polite but direct and not diffident.