KLM does appear to be bookable for the winter, although the timetables may not be up to date yet:
https://gyazo.com/839e45f9dfa0d3364fbe6fc5e99253e1
As for Aer Lingus, you can do a group booking for up to 25 people on their website, so I just tried that for a few dates in the first couple of weeks to see how the first flights were doing. Not the most scientific approach, but it gives a vague idea!