The Riddle of the Sands (this year's beach book, thanks macausland!) does have a fine word play on Böehme which Davies writes as Burmah. The seven islands/ seven channels off Friesland could be seen as the main characters. There's no equivalent off the East Anglian coast though the purported invasion point, around the Wash, is pretty strange e.g. Blakeney Point
There's also the so-called Scolt Head Island, an offshore barrier island just west of Wells-next-the-Sea.
It is accessible at low tide and seems to shift about according to wiki...
The shingle and sand island appears to have originated from a former spit extending from the coast, and longshore drift means that it is slowly moving to the west and inshore.But further on we're told
It was originally thought that the island, believed to be 2–3 thousand years old, developed from an offshore shingle ridge, and had thus always been an island, but current thinking is that the island was originally a spit extending west from Holkham dunes. Support for this theory comes from boreholes and from radiocarbon dating of a shell to 837AD, that appeared to indicate the existence of saltmarshes behind the shingle barrier at that time. which is mightily confusing.