Southampton could be a busy place for paddle steamers, as can be seen from this undated postcard.
As far as I can identify them, the paddle steamers from left to right are:
PS Queen, PS Princess Mary, PS Princess Helena (or Her Majesty?), PS Solent Queen, PS Prince of Wales(?), PS Princess Beatrice (?), PS Balmoral (?) and PS Lorna Doone. If you can confirm (or otherwise) my suggestions please let me know. tom.lee@virgin.net.