derating

I'm currently renovating a my new home which is a late Victorian house, and I've taken plaster off a couple of stud walls in my office. With in the room, there are currently (The house was rewired around 7 years ago). 1 Run of 1.5mm T + E for the lighting Circuit (running from floor to ceiling...

After a bit of initial advice, please. Decided to internally insulate a solid brick outbuilding as it's freezing in winter... in the process will be needing to move and add more electrical sockets etc, going to use said building for general craft/diy type projects. I had intended to build...