Hi wildemon, we've looked at the hydro stops from metafix, about 35 quid each, should be good value if they stop a floor flooding. They seem to work pretty well from the limited testing we did, just require a couple of double a's to operate...
We use the Matafix devices too. They have saved us from a couple of floods. We change the batteries yearly on service - so far no problems. They aren't suitable for feeding a booster pump as the suction causes them to close.