Nymph, Fairy, and Witch were Boats operated by the Woolwich Steam Packet Company

Reference:
Dix, F Royal River Highway, A history of the passenger boats and services on the river Thames. (Newton Abbot, David & Charles, 1985) pp 239,253, and 271

Two rivals of the Watermen’s company fit the description “black funnels”; the Margate and London Steam Packet Company and the City Steam Packet Company

Reference:
Dix, F Royal River Highway, A history of the passenger boats and services on the river Thames. (Newton Abbot, David & Charles, 1985) p64