Try here:
http://www.caa.co.uk/docs/122/summar..._transport.pdf
It is a CAA document with a summary of the definition of Public Transport extracted from the ANO.
It says:
5.5.3 ...... In particular, a member of the group cannot pay an instructor to train him in the group owned aircraft. (However, see AIC 7/2004 (White 94) which allows a joint owner to undertake flight tests and pilot licence renewal/revalidation flights.)
I hope this helps.
Regards,
ifitaint....