The guys in Frasier are supposed to have a bit of that snooty Boston accent, but more so the younger brother...
On the accent thing. There are websites out there for help on this kind of thing, but I couldn't tell you which to use. As an US-dude, in the main what you will need to be able to do to help you in the quest for a brit accent is reduce the pronouncement of your "R"s when you talk. It's one of the consternent sounds Americans seem to be generally big on.
I hate generalising, but that's what I'm saying. I could do a gobbledy-gook voice of nothing but "R"s (of various pitch) and sound vaguely American to a non-english speaking person. I once convinced a room of people that I could speak fluent Italian (my italian is basic), until a European who knew 6 languages exposed me.
like any accent, focus on the reoccuring particulars of vowels but mainly consternants (they are the tools of articulation).