Gunners Park
Partly a former MOD site it is now surrounded with modern houses where the ‘gun’ sits rather oddly. Plenty of free parking but no ‘facilities’. Unless you continue out onto the promenade back towards Thorpe Bay
https://www.tripadvisor.co.uk/Attraction_Review-g503790-d4062553-Reviews-Gunners_Park-Southend_on_Sea_Essex_England.html