Noelwj,
Perhaps the confusion comes from your location. Your location is given as Northern Ireland.
UK rules according to the posters above is ss+30min.
However I am sure that if you are based in NI, that you often fly into the Republic, and that you come across many pilots based in the Republic. The night rules in the Republic are different.
In the Republic of Ireland, from 1 April to 30 Sept, night starts at ss+30 minutes. From 1 Oct to 31 March, night starts from sunset.
Perhaps that helps clear up the confusion?
dp