The Society of Genealogists (SoG) is holding a sale of some of the duplicated books in its Library. I've run through the more than 200 books on the 'sale shelf', and found the following titles of direct Irish interest:
Funeral Register of the First Presbyterian Church of Belfast 1712-36, £6
Gravestone Inscriptions; Belfast; Vol 1, £7.50
Old Irish Graveyards: County Leitrim Part III, £2
Old Irish Graveyards: County Sligo Part 4, £2
The Ancient Celts; Second Edition, £10
There are also many other books covering histories of counties and cities, family pedigrees and histories, Whitaker's Almanacks, Army Lists, biographies, indexes to wills, graveyard inscriptions etc that will be useful to family historians with connections across Britain.
Funds released from this sale are used for the conservation costs of some of the treasures the SoG holds in its Special Collections.
You'll find details on the SoG website.