Possibly - probably, even - but not definitively so. Certainly I can imagine that perfectly devout Hindus, Muslims or Anglicans could be unhappy at overt proselytising from their Catholic friends, for instance.
Must say I've never met an Anglican, or Protestant for that matter, who has been unhappy at overt proselytising from Catholics - they usually simply argue back. As for Muslims and Hindus, when were they believers in the sense I use the word - ie followers of Christ?
Genuinely, here, I wasn't aware that the law made a judgement on what was a Christian faith and what wasn't, do you have a reference source I could look at regarding that?
Sorry, O, I was working on outdated info., which I should have remembered changed in 2012. Until then all churches/
Christian places of worship were 'excepted' in terms of charity status and some other tax issues, and came under the auspices of their denominational organisation - the Baptist Union of Great Britain, the Church of England, etc..
In 2012, each congregation (unless they had an annual income of less than £5K had to register individually). The JWs and Mormons have never had that 'exception' ruling, something that they have been frustrated by.
The only way I have sourced this is by trawling though the Charities Commission site.