Re-Acclimatised back in UK
 

Having been away down route from the UK (UK AOC op) for 5 days (Sri Lanka utc+5hrs ) how many local nights Off do you need once back in the UK prior to becoming re-acclimatized in the UK/UTC zone??? and available again??

Same as anywhere else, 3 local nights on the ground with uninterrupted rest. Assuming you are working under UK rules... You can work again after one minimum rest period but most airlines have policies about not using crew who are not acclimatised.