The aircraft has a MTOM of 600 kg and is Annex II listed. My friend is aware of the list of items which he's allowed to perform himself, although I wasn't aware that he could do the 5 yearly hose changes himself.
We have heard tales of engineers in more populated areas elsewhere who take a pragmatic view of the EASA permit and don't discourage owners from doing much of the maintenance themselves, treating it in a similar way to the LAA permit under their supervision.
I guess that it comes down to whether any engineer is willing to take upon himself the responsibility of signing for work done by the owner, some of which the engineer wouldn't be able to inspect closely after completion.