Hello Brian,
If at all possible these days .
Maybe if you could get hold of the following books.
The History of RAF Marine Craft 1918 - 1986, by Geoffrey D,Pilborough.
5 volumes.
Vol 1 - 1918 - 1939
Vol 2 - 1939 - 1945
Vol 3 - 1946 - 1959
Vol 4 - High Speed Launch 100(A)
Vol 5 - The 200 Class Seaplane Tenders(B).
Also the National Archives AIR 29 series may help,
AIR29/441,
446
448,
449,
450,
452,
893,
894,
903,
910,
915,
917,
920,
950,
and others.
https://discovery.nationalarchives.g...a+Rescue+Units
Alex