From south woodham ferrers to Burnham (or the other way) is a good walk you have to come inland on the section near SWF.
Also the Bradwell area is nice there is a section from St Peters Chappel to Bradwell, from Sandbeach to Burnham there is a stretch of about 12 mies with no habitation or shelter a beautiful walk, also walking round the edge of Mersea island is about 12.5 miles and a great walk on a fine day.
Leigh on sea, Southend on Sea, Wakering and Shoeburyness are all regular walks as I have family over that way but I have yet to walk at the naze peninsula