Strange, as the thermal blocks used for internal walls will expand
when they get wet and contract again when they dry out, which sounds
like it would be really bad news in foundations below the damp proof
course. (You have to be careful plastering them for this reason.)

I have to say that I did not consider celcon thermal blocks to BE
concrete actually.

Clearly, the manufacturer disagress, though!

http://celcon.co.uk/index.php?do=Page&pid=146

Christian.