Looking at your map again and assuming that it is orientated north/south, then there are four stones in alignment with the general alignment of the Thornborough Henges and that is SE to NW. At the risk of being labelled a New Ager - this means that there is the possibility that the stone row and the henges all align with the winter solstice sunrise and summer solstice sunset. You could have a whole ritual landscape at risk.

Francis Pryor is hot on ritual landscapes and it might be worth trying to contact him at Flag Fen. The campaign could do with a well known name or two to help it along. The stones have gone and their location underwater (judging by the OS map) so you cannot give archaeological proof. You do have enough to warrant serious further investigation before more of the area is chewed up and drowned.