Kelvin - you can see the current position of the Jet Stream here
https://www.netweather.tv/charts-and-data/jetstream
At present it is situated in the northern part of the Atlantic, which would explain why everything going West is routing on more Southerly tracks. There would still be several tracks available, with the departures routing over Bristol and S Wales taking the more Northerly tracks.
Flights going to the West Coast were taking routes over Greenland to avoid the Jetstream to the North; these would be taking an initial path directly to the North after departure, rather than a more NW track over Belfast.