Being vegetarian Hong Kong, London, Sydney.?

I am in my first year of University in Toronto. I have been vegetarian, (Lacto-ovo), since I moved here in September and I haven't found it challenging at all. I want to do an exchange year abroad for sure but I'm having trouble deciding where. My top three cities are Hong Kong, London, and Sydney. Please let me know if you have been vegetarian in any of these cities and how available vegetarian options are. Thanks.