I'm surprised you have so much trouble with counterfeit coins etc. I'm not sure I can ever remember being handed counterfeit money in more years than I'll admit to.

Having said that, I have noticed that some retailers in the dodgier bits of London are using note checkers more extensively - but they haven't spread to areas where tourists are likely to be - and I would imagine that tourists are more vulnerable as they don't really have a good feel for the currency.