We are midway through renovating a 1930s house and currently have booking for bead type cavity wall insulation on external walls in the house. The problem is that later on we are planning to replace the external doors and door frames which have gone rotten (including a large front door). Generally speaking, is it likely that once door frames are out, the cavity is exposed and if so is it likely that we'll get insulation material everywhere and cold spot above the door? Cavity is 50mm.