Can we go back to the business trip thing a bit!
As I understand it - as long as you do not accept financial reward (other than "cost sharing") and are within the 90 day rule then you can take passengers under a PPL to any destination you could otherwise take youself. The reason for taking them there - their choice, your choice, their business, your business or whatever - is,
AFAIK, not relevant.
It may be diffrerent in the US, as the first poster on this sub-topic suggested, but if there is a rule out there in CAA or JAA regulations I have missed that limits passenger flying from the above, then please enlighten me.
Ali