In this video by José Rodríguez, Managing Director of Visiting Angels Barnet & Enfield, he explains the pros and cons between using a private carer and using a care agency. He also touches upon what you should do if you already have private care in place but could do with a little more support.
A table summarising the pros and cons of choosing either a private carer or a carer through a care agency can be downloaded as a PDF or can be viewed below: 
The above table, however, is not currently accessible for blind or visually impaired people. Therefore, to hear its content, please refer to the video above.
Some of the websites where you can check agencies’ ratings, including our own, are listed below:
https://www.ageuk.org.uk/information-advice/care/arranging-care/