You would require a technician to visit and install the second box. The technician will be able to make up a cable as long as required. You would not be able to do a self install as the self install cables are only a couple of meters long.
The cable would probably be run around the outside of the house as long as it's not a mid terrace. If mid terrace you would need to have the cable run through the inside.
It depends on the cable run, shorter is better as 35m can be a lot if your house is far from the cabinet as the signal losses caused by splitting the cable and the length of the cable may result in inadequate signal strength for the second box. It would help if you could drill the holes for an optimal routing and install a pull rope for the cable. If you order a V6 the same routing should be used for an Ethernet cable.