Whose Job is This?

My plumber has just put in the Shower trays and freed the pipes for radiators in the bathrooms of our new build.
There are now obviously holes around where the radiator pipes have been dug out and there is a gap and hole between the rest of the bathroom floor and the shower trays.
My question: Who normally fills these spaces with concrete? Is it the plumber, the tiler or as I fear down to myself.

When you say a new build do you mean a self-build or is there a 'builder' with overall responsibility? If there is a builder, I would imagine its his job, but if not, then its you own look out I would say! neither the plumber nor the tiler would take responsibility in any case...