These poor sirens are likely to be scrapped soon. I think they are all of the Castle Castings type, ex-air raid, been used for flood sirens for yonks. There's 10 of them in Canvey Island and there is a list here:
clicky

Corner of Maurice Road and High Street by charliejohnson19, on Flickr

Corner of Maurice Road and High Street by charliejohnson19, on Flickr

Charfleet Service Road by charliejohnson19, on Flickr

Station Approach corner of a playing field by charliejohnson19, on Flickr
A few of these were taken from inside the car so not too great.
The situation with these is the dumb councils reckon they can replace them with text and radio alerts only. Hahahaha!