they could drive piles in, and construct a curtain around the crumbling coastline... and fill it with concrete !! would probably cost more than the house though!?!!
there was a story on 'homes from hell' where an old couple who had lived in a house for years close to a cliff edge suffered the same problem, they had to move out for safety reasons and the house became 'worth less'
they had a house going to ruin, they couldnt sell or live in.