The idea has been put forward a few times by loyalists. The first I've seen of it came from unionist opponents of the welfare state who suggested forming an independent Ulster in the Commonwealth rather than implement it.

In the 1970s the idea had some currency among members of the Ulster Vanguard movement (a breakaway from the Ulster Unionist Party). These people believed Britain was not serious about stopping the IRA and was preparing to betray Northern Ireland.

In terms of solving the conflict, proponents of an independent Northern Ireland have usually proposed a hard-line security response which they accused the British state of shirking.

An opinion poll in 1981 found only 14% support for independence in Northern Ireland but 37% of British people supported the idea.

Source www.Cain.ulst.ac.uk