Khaosai,
It was not restricted to the Virgin Sun operation. Guys with very little seniority were kept on the 747-400 as cover whilst fleet cross trg was carried out. More senior pilots who were still below the chop line but on the wrong fleet were let go straight away. It was seen as a necessity to keep the fleets crewed whilst all this cross training occurred. Things improved a little quicker than thought, whilst these junior guys were still at VA so they were not made redundant. Therefore LIFO was not strictly followed.
BTW all the pilots flying for Virgin Sun were employed by Virgin Atlantic with Virgin seniority numbers.