Insulating around radiator pipes and junction boxes?

I have 1920's house with a suspended timber floor. I was thinking of adding Kingspan/Celotex 100mm insulation in between the joists. However, I have electrical junction boxes attached to the joists and also pipework going through and above the joist in a few places. What's general consensus around installing insulation around the electrical junction boxes and heating pipe in regards to fire safety. Any pointers would be hugely appreciated?