I don't know of any others apart from those at Old Felixstowe, Shingle Street and Dunwich Heath, there are some at Aldeburgh but I have no knowledge of these.
The Cottages on the cliffs at Dunwich Heath must now be in danger of coming to some grief with the eroding cliffs, if you do get the opportunity of visiting when the heather is out in July/August you will be in for this type of treat
This is also one of the very few places in the UK that you can almost certainly see the Dartford Warbler