My solid brick 1800s house in south Britain, it is semi detached. I am considering internal insulating some of the walls on the detached size to reduce heat loss a little. The idea would be to simply attach something to the plaster walls, possibly plasterboard over and adjust the skirting board, electrical sockets accordingly
I don't want to lose much space so what is an effective thin material I can use. I'm happy to pay more for a more expensive material to reduce the thickness required.