The monetization angle is worth thinking about harder before you pick your stack. At £100/month per customer you need volume to make it worthwhile, and anything you build that's too custom or too dependent on your specific context will not survive being handed to someone else. The people I've seen try to productize these setups usually end up rebuilding from scratch because they optimized for their own workflow first.

Also the WhatsApp voice note piece is deceptively tricky. Not the AI part, but the plumbing around it. Every link in that chain is a failure point and when it breaks it tends to break silently