Thanks Mick, I guess Ray has more information than he really wanted now!

My link above seems to have been renamed as Eighteenth Century Cheap Print, but it still doesn't give doesn't give much background information on the Eighteenth Century Short Title Catalogue Project, but according to the British Library;
"Originally, the catalogue was entitled the 'Eighteenth Century Short Title Catalogue', covering the period from 1701 to 1800. In 1987, the International Committee for the 'Eighteenth Century Short Title Catalogue' approved a plan to extend coverage retrospectively to the 15th century and the advent of printing in the British Isles. In 1989, the American team began work on pre-1701 material, and the resulting records were made publicly available in 1994. To reflect the expanded coverage, the database was renamed the 'English Short Title Catalogue'.