http://m.screwfix.com/p/helifix-crack-repair-helibar-6mm-x-1m-pack-of-10/84070?filtered=true Try these, I hear they work a treat.
a few cans of expanding foam will have that sorted there'll be a lot more founds dropping after the floods have gone, maybe not quite so extreme - time to stock up on stitching kits
I reckon just keep a close eye on it with them measuring gauges , and if it doesn't move any further...