Just to reinforce what FNG wrote, there is no significant difference between company and joint ownership for the purposes of the PT/aerial-work/private rules set out in Art 130 of the ANO.
An aircraft can be operated on the private category in the conventional way that groups operate (pilot pays hourly and monthly costs) by either up to 20 joint owner-pilots or by a company of which the pilots each own at least 5%.
With more than 20 owners, whether a company or not, the aircraft has to be on a PT C of A.