I am manufacturing composite sandwich panels for floor and firewall panels in a Formula Student race car.

Does anybody know if Nomex can be laser cut so i can accurately cut my core to size. This will also help more more accurately position aluminium inserts for mounting.

I've never done it myself but I've heard of it being laser cut.  Unless it's very dense honeycomb, a razor knife might be better.  Honeycomb edges aren't super rugged - they paper just pushes/collapses - so it may not give you the kind of tight fit for an insert you'd get with foam.  It is also common practice to insert foam or taper back to solid laminate around a metal insert or fastener hole in honeycomb core.