We only have one species in Britain, and they are only here by human introduction. Escaped/released captive individuals or pets. They make a welcome addition to our fauna I think. Although there is some concern over their increasing numbers they seem to have found their own niche and are not thought to be directly pushing out any of our native species. They are extremely well established now around London, but are spreading much further afield too. You can hear their distinctive calls all over the place in London.