Green’s Dictionary of Slang

the expatriate Irish people living in the UK, esp. those who have prospered; also attrib.

1995		Irish Times 6 Mar. n.p.: A leading member of London’s ‘Murphia’, the group of high-profile Irish who have made good [BS].
1996		F. Wheen Lord Gnome’s Literary Companion 337: His deepest suspicion is reserved for an imagined literary mafia and members of his own ‘murphia’, like fellow ex-bank clerk Terry Wogan.
1997		Irish Times 11 Jan. 🌐 The opening night [...] at the National Theatre on London’s South Bank this week was like a Murphia magnet – the small theatre was packed with Irish people .
1998		(con. c.1962) E. Klein Just Jackie 27: Her poll numbers were sky high, higher even than Jack’s; this [...] impressed his Irish mafia (‘the Murphia,’ she called them).