You are fortunate indeed to have such a wealth of the Toadflax brocade moth caterpillar (Calophasia lunula) on your doorstep (literally). This species is classified as rare in Britain. It colonised Britain relatively recently (1950), but now appears to be in decline. It is found in a relatively small number of sites including a number in Greater London, along the Kent and Sussex coastline, and was historically recorded from Essex. The species has been observed in most European countries and has become established in North America following an introduction.
As this moth is at the northern extreme of its range in the UK, it seems that climatic factors are the major reason that its distribution here is so restricted. In periods of poor weather, the range often decreases. In addition to this, the remaining coastal shingle habitat is under pressure from development and coastal defence work.
Have a look at the distribution map on the NBN and make sure your population is recorded with GiGL http://www.searchnbn.net/gridMap/gridMap.jsp?allDs=1&srchSpKey=NBNSYS0000006316.
Take good care of your brood..... it sounds as if you are doing a pretty good job!
Oh what a shame , especially after all your hard work.
Today we spotted 5 more of the caterpillars, on a clump of yellow Toadflax, literally round the corner from where we saw the one (on a wall) the other day. We ran back home for the camera to take photographic evidence.
We looked at the map link on the reply to your original post and there was no red box anywhere near where we live. Do you think anyone will see this and update the map?
We are going to try and source some Toadflax plants for our garden now!