Fascinating photos, Colin, a real find. Reference the vessel in #5 with L Savile on the side, have been for a Google and found some interesting stuff. I could see that she was a tender so that gave me a good start (see that Bob came to the same conclusion).
She is a real old veteran built for the Great Western Railway in 1891 as a liner tender, ferrying passengers to and from passenger liners at anchor in Plymouth sound. She was named the Sir Richard Grenville and then briefly the Penlee before being purchased by Dover Harbour Board in 1931 and renamed the Lady Savile.
She would have performed the same function in Dover, ferrying passengers and mail to and from passenger liners calling in briefly en route to New York or wherever.
Your photo shows her in 1946 after completion of war service. Where she went during the war I know not but there is a reference to a "Lady Saville" at Greenock under "various craft" allocated to Western Approaches Command, which may possibly be her.
DHB sold her in 1947 to the Essex Yacht Club who used her as their headquarters until 1975 when she was replaced by another Dover veteran, the Trinity House pilot cutter "Bembridge," and went off to the breaker's yard at Queenborough.
At the Essex Yacht Club:
The arrival of Bembridge:
Plus very interesting article and close-up on this site:
http://www.dover.freeuk.com/port/commercial_harbour.htm