First things first - what counts as flyable weather? Generally in schools across Ireland you go out and fly as long as the cross wind component doesn't exceed 13-15 kt and head wind component has no gusts, so pretty much if it's coming down the runway anywhere up to 20kt, it's flyable. Cloud - ovc at 1800ft is fine as long as the visibility is ok and there's no percipitation. It's very rarely fully ovc, most of the times you can either get a decent vfr on top or large enough breaks to fly at decent altitudes
It's a very tough question to answer - UK/Ireland and Western Europe in general is in the receiving end of the Traveling Low/prevailing Westerly zone. Our climate will be impacted by the amount of energy stored in the Atlantic, and the global events such as El Niņo /El Ninja. What it means is that good, dry, sunny summers are interchanged by wet and windy ones. Last summer I flew every weekend from March to October no issues. This summer, albeit warmer, had a lot of foggy, drizzly days and I didn't flew as much as I wanted. Winters can be a bit hit and miss as well - last winter brought storm after storm, rains, floods, full package of never ending misery. No flying from October til February at all.. This year is shaping up very differently, today is definitely flyable, tomorrow promises to be reasonable as well.. who knows what December will bring, some people insist we will see snow. If the high pressure sets in with a nice northerly/easterly flow, we might see very cold, but beautiful days of flying