Im no expert but you dont need to polish every week, the trick is, polish THEN wax, and its the wax that will last a while, normally anything from a few weeks up to a good few months depending on the wax.

Id use something like this for polish http://www.cleanyourcar.co.uk/polish...h/prod_44.html
This for wax http://www.cleanyourcar.co.uk/wax/co.../prod_207.html

That Collinite wax is meant to be the best stuff you can get