The age of H4a1a, i.e. when it split from H4a1, was estimated as 7385 years, with a standard deviation of 1647.4, in the recent paper: Behar, et al. (2012), "A 'Copernican' Reassessment of the Human Mitochondrial DNA Tree from its Root" (available online for free at http://www.cell.com/AJHG/abstract/S0002-9297%2812%2900146-2). So it's much older than any independent identities of Norwegian, English, or Irish.