If your house was built before 1920, it’s likely to have external walls that are solid rather than being made up of two layers with a gap in-between. Unfortunately, more heat escapes through solid walls than those with cavities, which means you’ll feel the cold more and you’ll struggle to keep your fuel bills from rising.
As well as insulating your home on the outside with external wall insulation, there is the option of insulating your home from the inside with internal wall insulation. This is done by installing rigid insulation boards to the walls, made up of plasterboard backed with rigid insulation ranging from 60-100mm in thickness, then plastered over so you can repaint.