I am finally back in London and I can start working on the site more regularly. For a start, I wrote a page with advices on how to reduce your accent: https://voicecoach.ai/how-to-reduce-your-accent
I went through most of the available online resources and shared them along with my own ones as I have been trying to improve for many years.
I believe a lot of the software tools I might be creating can be used to help people improve their accent.
In addition, I have used ads (minimum budget per day) to bring traffic to my website and especially get people to use my voice recorder more, which helps me collect feedback on how to improve. So far, solely judging by page views, bing ads are much more effective than google ones.