Very pleasant short trip to Whitstable yesterday. What I did note is that there is a boat trip into the Thames where there are defensive forts positioned, like the battery at Grain but there are 6 or 7 of them clustered 6-miles off shore. Price is shown on their leaflets at £40 for a 1-hour trip but they will be contacting me for a potentially dedicated one for OPS.
Checkout their Facebook page and pls give an indication if you'd like to go.
https://www.facebook.com/search/top/?q=whitstable%20boat%20trips&epa=SEARCH_BOX