There's a use of
Konjunktiv meaning politeness:
Ich hätte gerne (…)
First, I wish to know why does this form denotes Höfflichkeit. (My only guess –influenced by my native language– is that this form is used as a the tacit preamble in brackets:
[Wenn Sie das mir geben wollen,] hätte ich gerne (…)
instead of giving an order.)
Secondly, if this "being kind" is reciprocal, that is, if the person who is offering a service says e.g.
Hätten Sie gerne (…) ?
which effect does it have? The same politeness or is actually an undecisive way of offering something?