I had a response to my complaint:
"Thank you for writing to Amazon.co.uk. We value all feedback from our customers and your correspondence has been forwarded to the relevant team internally.
We rely on the Charity Commission, the official charity regulator in England and Wales, to determine which organisations are eligible to participate. If a charity no longer has charitable status and has been removed from the Commission’s register, we will remove them from the service. The organisation in question is approved by the Charity Commission, however, due to the serious nature of these concerns, we have referred these allegations to the Commission and will be conducting a full review to ensure they do not violate our policies."
In a nutshell I said I had safeguarding concerns about their online chat facility and that they appeared to go against the NHS 'watchful waiting' approach.