I asked roughly this a short while back, and then I asked the CAA, who said that a CAA (not EASA) aircraft such as a PA28 not used for public paid transport is covered in Article 34 and Schedule 6 of the ANO. I realise that doesn't quite help in your case, but it may give some guidance.
http://www.caa.co.uk/docs/33/CAP393.pdf
CAA aircraft not covered by an AOC don't need a tech log, just the requirements above. As for EASA....?
The man at the CAA to ask is Neil Williams -
[email protected]
B