Whether you drive that vehicle for 5 minutes or 5 months, if your work involves “collecting/delivering” for the purposes of commerce (related) then you need Driver CPC.
Private use: No Driver CPC.
Commercial use (in this instance) Driver CPC.
Don’t relay on calling the DVSA or DVLA. You are calling a call center and most of the staff are reading guidance of the internet. You can get a different answer depending on who you are speaking to!