Hi
192 / FindMyPast [ the most common refs made here ] are not the only websites for finding near-years living people.
Sites like !stlocate are currently "better at it" [ other sites and procedures are available ]
If people are not deliberately hiding [ and are in uk, alive ] then the odds are they can be found.
The "problem" with sites like RootsChat is that their policies include privacy for living persons.
[ Quite correct in my view ]
Sites akin to Facebook / linkedin {etc., etc..} work very well.
Open letters may be the wrong approach for some.
The target person may have hidden their past and not wish to be contacted . . . . .
Sometimes you just have to resort to using professionals.
Ray