Thanks for your help. I have used something like you describe to stop it from falling through but there is nothing to stop the whole assembly from being lifted up i.e. I need something to fix in place underneath too.
I am in exactly the same sitution. I bought a Liscia shower tap (designed to go over the bath) and replaced a large single hole tap in a new build apartment. Did you find a solution and could possibly advise me? Thanks.
