I think it really depends on where you're from. I've been hopelessly trying to teach my wife 'perfect' English pronunciation at her request, and the best advice I came up with is to talk with your throat and not your mouth. At least in the Southeast, this works almost perfectly. But we say 'loo' if anything at all, it's a pretty rare word.

From my experience, the more north you go the more you talk with your tongue/mouth. In my examples I was almost able to complete full sentences without moving my lips at all.