Cobbled together a rough and incomplete list, with types where they're mentioned.

Alderney (16 turrets, 7 with 3.7cm & MG, 9 with just 3.7)
Guernsey (c.30, 20XFT17)
Jersey (61)
Utah (many)
Omaha (??)
Juno (2-3?)
Sword (handful??)
Belgium & Netherlands (c.4000 ringstande, but no data on how many carried turrets)
Denmark (c.169-194.)
Norway (151+)
Spanish border (2Xpz.38t 18XPz.1&2 planned but a handful completed)
Eastern Front Total (c.694)
Soviet Union (c.1830
Poland (fair few, many captured T34 turms, no specific data.)
Germany (Many, no specific data)
Italy (191 in total, 91+pz.I turrets, many Pantherturm, possibly many more Italian turrets though it's uncertain these were finished)
Balkans (409 turrets, mostly Pz.1&2)
North Africa (Dug in Matildas)
West Wall
Finland (Many, primarily captured Soviet types)
Far East (Handful of dug in Ha-go & Chi-ha)

The above doesn't include the Sockellafetten mounts of tank guns.

Panther turrets specifically:
Stahluntersatz (metal base).
Atlantic/West wall - 119
Italy - 18
East - 6
Total - 143

Betonsockel (concrete)
Atlantic/West wall - 63
Italy - 30
East - 30
Schools/Experimental - 2
Total - 125

Overall Panther total - 268.

Cheers,
Adam