Hi,
Sounds like your floor is expanding with the heat. You absollutely should not have wooden floor fitting tight to radiator pipes...also check if an expansion gap has been maintained around the perimeter of the floor.
There should be at 10-15mm gap. were the skirts removed and refitted? was...
I presume you have a floor void under your joists. If you have 6" joists then i'd get some kingspan (or celotext...it a bit cheaper) and cut to fit between the joists. 100mm thick should be OK. Fit it tight and fill any gaps with expanding foam.