Vegetableman

Plasterboard is fire resistant but you will need to seal the gap between the wall and the plasterboard. This stops the heat getting between the chimney breast and plasterboard. I know this as I have just done the same thing! I'm just trying to find what sealant to use. I think this may do the trick. https://vault1.secured-url.com/chimney/acatalog/Index_Page_Silicone_Sealants_and_Caulking_Compounds_145.html