I used Avios on Aer Lingus Boston to Dublin as it was less than NYC and the flight from Philly to Boston was cheaper than getting to JFK. Only concern is have for January is potential snow PHL/NYC/BOS for a potential connection so while more expensive to LHR the direct flight might be good option and then LCC from LHR.

I have many Dublin posts on philatravelgirl.com (Jameson Whiskey tasting, Guinness storehouse, Westin review and The Morrison, a Doubletree hotel review, Photo tours, Wild Wicklow tour, etc) and my Irish blogger friend Susan writes at VibrantIreland and lives in Ireland is a good resource.

On a prior trip I enjoyed the Dingle Peninsula and the town of Galway but not sure of visiting in winter.

Rail tours Ireland has one day and multi day tours so you don't need to drive.

If interested in a private photo/tour of Dublin and South Coast, my friend Dave runs Dawn2Dusk tours which was a highlight of my visit and I've recommended to others.

Hope this is helpful start, DM with other queries.