Don't have the exact reference to hand but if you are carrying the aircraft logbooks in the aircraft they have to be in a fireproof container.
The journey / tech log being carried on the aircraft is no problem. It is best to have a method of ensuring that the most up-to date info from that tech log is left with a responsible person.
For commercial operators, this done by having self copying removeable pages or pieces of a page that can be removed.
For the small operator - simply use a serialed A4 sheet and copy it before departure. Leave the copy with the handling agent. Never carry old sheets - keep them at base.
If the aircraft is on a PT C of A then the tech log is a requirement. Is the CAA ever going to see that PPL club/group flying is not public transport?
Regards,
DFC