No- Coleraine Library will not be able to sell the microfilms- they are bought from PRONI by the Coleraine branch of the North of Ireland Family History Society, If you do wish to purchsed the church records you will have to contact PRONI (I believe you also have to get formal permission from the clergyman of the church but PRONI will explain the procedure).
PS- 1831 only lists head of household with numbers of males & females in household with a breakdown of religion Catholic, Established Church, Presbyterian, other.