There are a large number of gaming clubs across northern Ireland as Pyreguard already mentioned Lisburn Gaming club is one of the biggest.
I don't know what the
40k scene is like but you should also check out QUB dragonslayers. They are the gaming society for Queens University and are responsible for putting together the largest gaming and Anime convention in Northern Ireland every year Q-con.
http://www.q-con.org.uk/ There will be a 2 day tournament on the Saturday and Sunday of Q-con (29th and 30th) so I would recomend you book them off if you can ,even if you don't play it's a great way to meet people from all over.
If you're willing to travel there is a new Gaming centre opening in Newtownards called the North Down War Gaming centre. It's grand opening is April 13th and will be open 7 days a week with tables available for pre-book or simply turn up and play if tables are free. Their website currently has little to no information as they're still getting all that sorted
http://northdownwargamingcentre.co.uk/
Slightly further out we have Escape Gaming club in Bangor. This club is owned by Gareth Richardson, owner or Replay Games
http://www.replaygameshop.com/ in high Street Bangor and is run by himself and a committee of members including myself. We run on a wednesday evening from 7.30 - 11.00 and Saturday from 11.00 - 5.00. We're also starting to get into running regular 1 day tournaments with occasional 2 days once we get the hang of things
https://www.facebook.com/events/126224324229860/
Also in Bangor we have the north Down Gaming hub run by Tom O reilly and Andrew Johnston. They don't meet on a regular basis from what I can tell but they do run semi regular tournaments and Events on Sundays. Their facebook group can be found here
https://www.facebook.com/groups/286981511386404/ and has members from all over the North.
If you're willing to travel to the Distant north we also have Hangar 18 Wargaming in Londonderry
https://www.facebook.com/groups/303372876413319/ These guys are affiliaites of CORE the university of Ulster, Magee Games and Anime Society.They mostly run on Saturdays and whenever CORE runs one of it's mini-cons ENCORE they will show up in support and run the wargaming side of things be it Malifaux, Warmachine, Flames of War or whatever.
I know I'm missing a few groups out (Yes there are more) but these are the ones I'm most familiar with through either being a member or simply having met a few of their members at events and such. The one thing you will not lack for in this country is a place to waragame
P.S. I haven't been to the
GW in castlecourt for a while but Cathy one of the staff occasionally shows up at our Wednesday nights and will no doubt be more than willing to point out any groups I have missed and when/where they meet.
P.P.S If anyone knows....what happened to the northern wasters or were they just folded into lisburn and other groups?