Two pilots could log P1 under FARs but I would suggest, that the CAA would view this very dimly indeed. In the US, one pilot could be under the hood for simulated IMC whilst the other pilot acts as safety pilot. I believe in this situation, the safety pilot is the legal PIC with repsonsibility for terrain avoidance and aircraft seperation while the pilot under the hood is the sole manipulator of the controls. Two pilots logging the same time for the purposes of hour buidling towards JAR licences should not be contemplating this approach.