I've seen it
There is indeed a Lancaster in the mud at Pegwell Bay. My dad took my brother and I to see it in about 1970 or 1971, when it was visible during a very, very low tide.
How did he know it was there? During the war he had been a flying controller at Manston at the time that it came down, knew that it had not been recovered and certainly knew the difference between a Lancaster and a Flying Fortress. He said that there were several aircraft in the bay.
Sadly he's not around to ask for more detail and I was fairly young at the time. I do recall it looked pretty battered, but complete. My brother wanted to haul it out and have it in the garden!
As I recall, my father's memory was jogged - and our expedition decided - when my brother found a picture of it in his Eagle annual (1967?). I bet all you boys have kept your annuals, so go and look it up.
WW