It's been some time since I held that position both in a rotary and then fixed wing charter firms. Both occasions involved interviews with the CAA FOI responsible for each Company and they seemed more interested in experience gained in those types of field (ops) and the support available within the Company for ensuring safe and legal operations.
I suppose for someone who has never been involved in charter ops and AOC's it could be worthwhile going on an ops specific course covering all AOC legislation etc, however as a nominated position I don't know if the CAA would still require you to have some hands on experience, I would do as Mighty Gem suggests and phone them, it is they who have to sign you off.