If a company decides to undertake ALL of its refurbishment work under a direct in-house, self delivery method does it automatically become responsible for the Employer, PD & PC duties under CDM2015.
You would certainly be the Client under CDM Regulations and there is nothing to prevent you from also being the Principal Contractor as well. In fact under CDM s 5(4) if the Client fails to appoint a PC then they are obliged to fulfil those duties themselves anyway.
The only issue to consider is whether you have the skills, knowledge and experience to perform the role of a PC or PD, as required by s8 (1), which clearly infers that the Client cannot accept such a ‘self appointment’ unless they fulfil these requirements.