Denis:
Check out the following website which contains a guide to British ceramic companies, their history, and trade and initial marks:
http://www.netcentral.co.uk/steveb/mark
According to the site William Fairbairns was associated with 3 different partnerships in Hanley:
1) Thomas Cooper 1863-1865
2) Ambrose Bevington & Co. 1871-1891
3) Hanley Porcelain 1891-1898
Hope this helps.
Erica Gibson
Lab Director, Sonoma State University