Usually from around 10.30 or so until dark-last week they were passing by my work every 20 mins or so.
Probably approach practise to R35 at Aldergrove,also saw them doing a few spiral decents over the Lough.

Flights out of BFS in helis/light aircraft heading in a Westerly direction stay to the right of the A26/M1 on the way out and route back on the left side.