In article
Mike Dodd wrote:
snip

Why can we buy frame fixings with a posidrive head significantly larger
than a "size 3" (whatever that is) - Wickes sell these, as do CPC (for
significantly less than the sheds); But at 17:00 on a Friday evening you
can't buy a suitable screwdriver? (the sheds only sell toy-screwdrivers,
it'd seem).

Did they not have the right size spiral ratchet or impact driver bit?
Those are what I tend to use for larger screws.