Have you considered gluing them on?

I don't really trust Gripfil and the like, I'm more a mechanical fixings codger, perhaps I should move with the times. Have you had success glueing?

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. 

Paslode and Spit nail guns are available.  It is making sure you have the correct type of nail so to speak.  Some will fire screwed nails which will let you fire in and unscrew out.  Points to consider is the material you are going into and the nail type.  For the most secure fixing for a skirting board consider glue and screw(or power nail from gun)

Try and avoid grip fills as they normally skin over very quickly.  Stixall Extreme Power Adhesive or equivelant work better and allow more time for positioning and such before they start to go off of cure. 

Thanks for your comments, very interesting, I definitely need to get modern!

I moved in here a couple of years ago and the rooms in question are cement rendered with a very soft cement based skim. I've never seen anything like it. The original part of the house that he hasn't badgered up is C16, presumably he thought it more in keeping - who knows?!

My concern with fixing the skirting with adhesives is that it may pull the powdery skim off the render.

Cheers G