On a very quick look around, this seems in part to support the 'monuments lost to the sea' thing - though not necessarily on clifftops.

http://www.eng-h.gov.uk/ArchRev/rev96_7/costa.htm

Thinking about it, common knowledge stuff like Seahenge & submerged villages etc off East Anglia would point at this anyway.

But it seems to me to also suggest that, if anything, the Medway monuments would have been further from the sea when they were built, not closer.

But then if you consider that, at least in medieval times, the Isle of Thanet at the tip of Kent was a distinct island it would suggest that the Medway monuments would have been nearer the coast.

See
http://www.open-sandwich.co.uk/page2.htm and use the 'Click Here for map of the old coastline' link.

Oh I don't bloody know.

love

M