Hi Jenny
Came across an old edition of "North Irish Roots" this evening under my stairs, it is dated Winter 1987. In it there are some directories for Donaghadee and I noticed some names that may be interesting to you.
Belfast Post Office Directory 1843
Maxwell Charles, wine and spirit merchant
Slaters Directory 1846
Maxwell Mrs, Charles, Main Street - Gentry & Clergy
Maxwell, Robert, Bow Lane, Car Owner
Maxwell, Samuel, Sandy Row, Car Owner
And curiously!
Stevenson, Charles Maxwell, wine and spirit merchant (see above), New St
Stevenson, Charles Maxwell, Savings Bank Manager, New St.
Gary