Valuable consideration is a difficult concept and it's often a question of reasonableness.
"Benefit in kind" (as you use it) presumably means that you give someone something that they would otherwise have to pay for. That can't be a complete definition. If I take friends flying, I'm giving them something that they would otherwise have had to pay for. Does that make the flight aerial work? I don't think so.
As part of a bigger scheme of things, some club-checkout set-ups might be construed differently. "PPLs: if you're current, check out a friend whose currency has lapsed and we'll give you 30 minutes flying absolutely free!". Now we're talking valuable consideration beyond simply the privilege of being pilot-in-command.