The main switch in the man cave consumer unit will also require to be swapped for a 40/45 amp double pole switch like this https://www.electricaldirect.co.uk/product/danson-40a-2-module-double-pole-switch-disconnector-878429?vat=1&pr=1&gclid=Cj0KCQjw6-SDBhCMARIsAGbI7Uh8HVaA2QSEzP1HKEcu47oSVCWNoUgNIAqvCA5zXytpgVzT0v5dNd8aAkD7EALw_wcB