Tex, that observation of gentleness versus brute force has now been tried by three of my carpenter colleagues, all report that it actually works! - even on those dreadfull extension lead reels we are often forced to use on site.
I just browsed a leading discount supplier and a 1 gang 13A single socket, white, can be had for £1.10; 2 gang £1.62, the MK branded items = £1.98 /£3.88. All discounted for quantity of course and next day delivery free with a minimum spend of £50.00 = US $75.00, an easy way to convince the wife to allow the purchase of new tools! These are all sturdy bakelite casings, as preferred by brit consumers. The red neon indicator types that I like seem to have been discontinued...
For georgian or victorian brass covers [ did they exist then?] , £4.67/£6.05, for real fancy brushed chrome, £13.00/£15.78.
And it's true, they do never seem to wear out. They just get replaced for the 'look' in redecorating/remodels, as they go slightly yellow after about twenty years!
Details of the 'safer' MK design from WIKI...
....
BS 1363 allows two methods of opening the shutters. The original method of using the earth pin is still used by most manufacturers, but MK sockets use a method which requires both the lower pins to be inserted at the same time. In more recent MK sockets all three pins of a plug must be inserted to open the shutters. (MK sockets have the MK logo on the front of the socket.) The MK method eliminates the danger associated with inserting a cover upside down, but is no protection against the type of cover which allows paper clips and needles to be inserted into the live parts. The safest option is to rely on the protection required by law in a BS 1363 socket, and not add any unnecessary and potentially dangerous plug in covers .... 
