Hiya Anna,
Griffith's Valuation of Dublin 1848-51 lists three or four guys named Saul in Dublin.
Thomas Saul, Heytesbury Street, St. Patricks, Dublin
Robert Saul, Mary's Lane, St. Michans, Dublin
Robert Saul, Greek Street, St. Michans, Dublin
Peter Saul, Glassamucky, Tallaght, Dublin
Shaw's 1850 Dublin City Directory lists two more ...
Robert, 3 Lurgan St (not listed at address)
Thomas, 1 and 2 High St (woollen draper)
I'm sorry I'm not able to find out much about bankers in Dublin in the 1700s but hope what I have found so far will be of some assistance.
Chris