Sea level rise predictions are exaggerated
"Professor Niklas Mörner, who has been studying sea level for a third of a century, says it is physically impossible for sea level to rise at much above its present rate, and he expects 4-8 inches of sea level rise this century, if anything rather below the rate of increase in the last century. In the 11,400 years since the end of the last Ice Age, sea level has risen at an average of 4 feet/century, though it is now rising much more slowly because very nearly all of the land-based ice that is at low enough latitudes and altitudes to melt has long since gone."
100m? I would suspect most of Brighton would in fact be gone unless the residents have all moved north to the downs!!! I believe the Amex is only 80m above sea level
As an aside, I have it on good authority that there have been large cliff falls at Birling Gap. Part of the cafe has been closed and the house nearest to the beach doesn't look like it has long left.