The safe assistance follows through from the Management Regs and is in essence the same understanding. If the person is in the employment of RP, it makes practical sense, providing that person is competent.
If the size or complex nature or the premises is such and person providing safety assistance is limited in terms of experience, knowledge, training etc then they would not be competent. In which case, it would be reasonable that assistance is brought in from outside the employment.
Please don't loose sight of the fact that the new Fire Safety Order is not new law, but law that is reformed from around 100 + existing bits of fire legislation. It has gone through the process of reform to primarily be less of a burden on business and commerce etc. Hence, the understanding of safety assistance is from the Management Regs.
Hope this helps.
Shaun