I suspect the NICE guidelines only require sharps boxes for those on injections and pumps not just BG testing.
The beancounters i.e., the CCGs seem to think that lancets are safe enough to dispose of in general waste but there are some lancets that are safe others are not, some have an end cap that is difficult to accidentally remove after use, others just have a small lump of plastic to push the used sharp into, the size and lack of complexity make the lancets cheaper to manufacture (less plastic and simpler injection moulds)
The only lancets that are absolutely safe to dispose of in general domestic waste are those in cartridge systems such as those that come with Roche or Mendor BG test kits