If you never carry a load or passengers in that employment then you’re exempt from the EU regs, do no Digi card required, you then come under GB domestic regs, but if you don’t drive for more than 4 hours per day and stay with 50km of base, then no records are required for that day, if it’s a no to either then you can fill out a logbook or put your Digi card in and set to out of scope
If you’re driving to and from pre booked tests then you’re exempt from the dcpc too