Hallo Westy,
Yes, your experience in your gliding club is the way it could go. I agree it may only be easy in a club setting, but I believe certain schools (i.e. commercial organizations) are doing it de facto here, although not necessarily calling it a mentoring scheme.
Ref. the collaborating, or, perhaps, 'peer to peer mentoring'!, I'm a fairly low hours {150 or so} PPL/IMC and very happy to do this when asked - cost share, etc.. I usually find, as well, that actually I'm quite happy to share costs and not do any of the actual flying, if other, perhaps more assertive, individuals want to do more than their share.
Interesting to note the take-up of the electronic writtens there: I think there could be advantages to such a scheme here.