I just fitted something to the wall using the supplied plugs and screws and came to the conclusion that the new (modern design) screws are not as good as the old ones as they have less taper and therefore - whilst they cut a thread in the plug - they don't open it out so that it tightens (wedges) itself into the drilled hole.
It feels like a good case for maintaining a stock of good old number 8 and
10 screws.Any comments?