Also need to quantify what you mean by warm, have you got a temperature probe to test the outside of the cable it would help to know how warm tha cable is. It may not be a worry if within tolerances.
The calculation tables for cable size in the Electrical Regulations allow for up to a certain working temperature. However saying that, if the supply cable is old as your description suggests then the insulation may not be up to todays specifications regarding working temperatures so I suggest you ask your local electricity supplier for advice.
The calculation tables for cable size in the Electrical Regulations allow for up to a certain working temperature. However saying that, if the supply cable is old as your description suggests then the insulation may not be up to todays specifications regarding working temperatures so I suggest you ask your local electricity supplier for advice.