There is 3 clubs in Ireland so you should be lucky enough to be fairly close to atleast one.
Northern Ireland :
www.badmcc.com
Great track, good few racers in Banbridge, NI.
Navan, Co.Meath :
www.nnn.ie
Good sized astro track with a good turn out.
Galway :
http://www.gmcc.info/
Grass track in Galway never been but ask for Pete he'll sort ya out.
Hope that helps.