You need to understand that you’re mixing up three different pieces of legislation here:
Your Carer work comes under Working Time Directive, link 1. There is no mention of POA being applicable
As far as I can see, all the time you spend on shift as a Carer, except for the 20 minute rest periods (WTD has different rest requirements to RTD), will be considered “work” as (i) you are paid for this time and (ii) you cannot “freely dispose” of your time to do something else, like leave your client in bed with his movie while you to go out to a pub, cinema or restaurant. Link 2 discusses care work (albeit though the authors of that link don’t understand the difference between “affect” and “effect” )
POA applies only to “in scope” work, ie being “in scope of EU Drivers Hours (aka 561/2006)” . Road Transport Directive is the applicable working time rules here, for what is termed “mobile workers”.
The document in link 3 is old, but it should help you understand things a bit better
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Working Time Directive
The Working Time Regulations 1998 -
Working Time re social care
https://activesocialcare.com/handbook/employment-law/working-time-regulations-hours-of-work-and-rest-breaks/ -
Road Transport Directive
https://downloads.tachomaster.co.uk/docs/Dft-RTD-download.pdf