I am a convert to glue having been a drill and screw disciple for many years. I have used expanding foam, make sure you use lots of weights to stop it pushing away from the wall, successfully and it was easy to remove the skirting using a thin scraper pushed down the back. Where I did not use the scraper plaster got pulled off the wall when removing. I still occasionally use a screw on very uneven walls but you have to make a decision on following the walls or keeping the skirting straight. I am doing a job at the moment and will be using a silicon adhesive, fortunately the walls are reasonable straight. I have seen the demos of silicon adhesives holding a heavy block to a wall with no problems. 

I am a convert to glue having been a drill and screw disciple for many years. I have used expanding foam, make sure you use lots of weights to stop it pushing away from the wall, successfully and it was easy to remove the skirting using a thin scraper pushed down the back. Where I did not use the scraper plaster got pulled off the wall when removing. I still occasionally use a screw on very uneven walls but you have to make a decision on following the walls or keeping the skirting straight. I am doing a job at the moment and will be using a silicon adhesive, fortunately the walls are reasonable straight. I have seen the demos of silicon adhesives holding a heavy block to a wall with no problems.