For what it is worth, Leslie Hunt's Veteran and Vintage Aircraft (Fourth Edition) of 1974 lists the worldwide survivors as:
Sunderlands - 5 (MR V ML824 at Hendon, Mk III ML796 at La Baule in France, MR V NZ4115/SZ584 at MOTAT, MR V NZ4112/VB881/RN272/6534M at Hobsonville Yacht Club New Zealand, and MR V NZ4414/SZ561 at Whangerei, New Zealand but at time rumoured to be moving to a Preservation Group in NSW Australia.
Sandringhams - 2 (both at Rose Bay, Sydney Harbour, Australia - VH-BRC - formerly Sunderland III JM715 and VH-BRF formerly Sunderland III ML814 - both at that time still flying with ANSETT)
Solents - 5 (one of 3 possible survivors on the River Tagus, Lisbon - either G-AHIN, G-ANYI or G-ABOL, others scrapped, Solent 4 ZK-AMO at MOTAT, Solent 2 ex-G-AHIO 'Somerset' and previously VH-TOD aand Solent 3 ex-G-AKNP and VH-TOB both at Richmond and allegedly owned by Howard Hughes.)
There are of course, lots on the bottom of the sea and lakes! There are reliable reports (by my father!)of dozens sunk (using small explosive charges to pierce the hulls) near Stranraer, Scotland, after WW2. A real rarity - Mark I Sunderland T9044 - was discovered by amateur divers at Pembroke Dock and was then sthe ubject of a Channel 4 UK TV 'Wreck Detectives' programme - quite a lot of it left intact although only an engine was raised.