In the process of changing a radiator and found that the old fixings were a
bit too flimsy for my liking.

The new one is a 2000x450 double convector so fairly heavy. There are
currently three battens with two wood screws each, the screws going through
the battens and into the thermalite. The battens and screws just about
fell out when I tried to remove the screws. All the vertical load seems to
have been carried by the plaster coat around the battens.

Whats the best wall fixing for this sort of load in thermalite?

Tim

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Please don't feed the trolls