Some ministers are very good about passing on queries to someone in the congregation/area who can help and others don't bother. Bear in mind they may have no interest in family history, not been in the area for very long or get so many requests they have a policy of not answering any of them. Also, some are in charge of 2 or more congregations which may not be that close to each other or where they live so they have little spare time.
It's not always the minister who deals with records/queries- could be Clerk of Session or other member of Committee.
If you do write a letter-
1) explain exactly what details you are looking for. "I'm searching for the baptism of my grandmother Mary Smith born around 1889" is better than "Can you tell me about my grandmother's family, her name was Mary Smith and she moved to England.)
2) ask if there's anyone in the congregation who might be able to help/look up the records if they are not able to do so. Some will pass your details to someone with the same name or who is a relation so doesn't hurt to suggest they might do so.
3) include an email address
4) ask if there's a charge- if there is they will tell you (a small donation is always welcome but doesn't guarantee informations)
Contact details for 2nd Ballybay-
http://www.presbyterianireland.org/congregations/ballybay2.html1st Ballybay, Derryvalley and Cahans are a joint charge so one person will be in charge of the records (also connected are Cootehill and Drumkeen).
Minister of Loughmore also has Crieve and Corlea.