Aldergrove had two air displays back in the 80's. Aircraft displays included Concorde, US A10's, Vulcan.
 
I miss the airshows at Ards. As you say, it was a decent venue with just the disadvantage of a short runway. Handy to get to and the show back on the VJ year with the Lynx doing the backflips was excellent. Superb May sunshine that year (got my face sunburnt looking up at the aircraft!)
 
One of my problems with airshows up on the north coast is the certain element of risk you get with the weather and line up. It's a fair old drive up there, and being September you either get an ok day, or a blustery day which is not that pleasant. I hate it when things don't show up and the same aircraft (e.g. Jet Provest, Tesco Eye in the Sky, etc) do another mini display.
 
Please note, I'm not having a particular go here - I'm just depressed at our lack of a decent show to look forward to each year.
 Concorde at BFS for an airshow... Impressive! Pitty Aer Lingus couldn't be convinced to provide an aircraft for a flypast or two; 
 Image on airliners.net
Image on airliners.net The airshows at both Newtownards and Eglington were fantastic, having runways allowed a proper display line to be set up, and walking around various aircraft was always nice as well. The same for St Angelo's although I only made it up there once for an airshow and queued up for a wee nosey around the Duxford based Catalina, G-PBYA. 
The weather in May and June generally seems to be the best with weather having faded by September meaning we're out of luck by the time of Portrush Airshow commences. I can only remember one weekend where weather was good during the show.  
Portrush seems to be the last viable place for an airshow in NI these days as the number of businesses who profit from the event is massive. If an airshow was to be held at Newtownards, Eglington, or Aldergrove, it would be hard for the government to justify holding airshows at such venues with a lack of local businesses about. But the fact that people can not be charged at portrush Airshow is a major downside.  
200,000 people attended one weekend a few years ago. Charging each person roughly between £5-£10, along with the sale of several thousand programmes, and you're talking a decent amount of cash to cover for the costs and you have a self sustainable airshow. 
I wonder if anyone has ever considered Langford Lodge as an airshow venue. It would've been a good option back when the UAS were based there. 
Dave