Am I right in assuming that such a duct could not go round lots of corners in the way the OP seems to be suggesting on his plan? Does the duct have to be entirely underground (or buried in floor) or can some of it be above floor level (which, again, is what the OP seems to be suggesting)?100% chances are you will be required to install a 32mm duct from outside to the new position, DNOs cannot joint cables in a property to extend them.
Kind Regards, John