To be a Co-pilot, you must be rated on type and the aircraft must have a certification requirement for a minimum of two pilots. I was referring to an aircraft certified for a minimum of one pilot where there are a number of scenarios in which two pilots may have an operating capacity, neither of which is P2. They invariably involve checks which can quite legally be conducted by a pilot who is qualified to fly the aircraft without any other qualifications. There is no difinitative answer to what you log, neither does there need to be. Log what you do, and if the CAA don't want to count it, its their perogative not to.