Hi. We are about to remove a warm air unit and replace it with boiler and radiators. Please see the pics. The two side walls are fine but the back wall is covered in what looks like concrete with the odd brick showing through in places and a hole that needs bricking up/covering. We need to make this wall good because it is going to have the new boiler bolted to it and will remain open so it will be seen. Just wondered if you could offer any advice on how best to make this good. A local builder suggested plywood or plasterboard but would this take the weight of the boiler. I am just thinking that there must be a common way of dealing with this, maybe fix the render and then plaster it or something. All three walls are solid brick. Thanks for your help.