I don't mean to p*** on anyone's party, but where I live, (but maybe not where PistonsDead lives) it is a requirement that if more than one consumer unit is connected to a main fuse, a single point of disconnection must be provided so that all the consumer units can be isolated from the supply by flipping one switch. Here's a picture of our installation after we had a second consumer unit fitted (indoors), showing the single isolator switch that was fitted at the same time. Might be worth checking whether this should have been done and get them back to do it if necessaryView attachment 433537
They fitted that as standard for me.