I think Whirlygig's view of the JAA/UK requirements is correct. The flying should be "incidental" to your employment. If not, you are being paid for flying and therefore need a CPL or ATPL.
Not sure if it is the same in other parts.
This does not mean that PPLs don't do what you say. Just that they haven't yet been caught.
With the CAA's track record for (non-) enforcement a PPL could proibably make a career of it unitl something went wrong