Question about the lack of Northern roles

Sorry if this is a dumb question from a non-British person: Why is there a lack of "Northern Coverage" in this show? Is that a norm in British politics? Sure those politicians are disconnected from the general public but why leaving northern people behind? By "Northern Coverage" I mean Northern Irish people and ppl from elsewhere in the UK.

(No offence but is that a social norm Northerners are not that involved in British politics "circle"? Please correct me if wrong)

Nevertheless the characters are mainly English except those two raised by Scottish wolves.

The closest I could relate are a) ^{Mary from the focus group} b) Julie the widow c) Steve Coogan's role from In The Loop. Plus, these actors are of Irish descent or background: Peter Capaldi, Rebecca Gethings and Michael Maloney.

Just to clarify I know certain basics bout Ireland, Northern Ireland, Britain n UK etc.

You have been lovely, thanks in advance.

THERE'S MORE TO TTOI DAN DIS.