You can't create a calendar invite in UTC. Period. This was a year ago; I don't remember the specifics, but either the invite I had was for UTC, and Google Calendar put it in in my own timezone, despite it being clearly UTC, or I had to enter it by hand, and there is no way to specify UTC/GMT by hand in Google calendar. The issue is not an import issue, it's that Google calendar literally does not have the option, at least that I can find. You have to select a region, and there is no special 'UTC' or 'GMT' region, and clicking on the UK does not give you "Greenwich" or "GMT" either.

Though per another comment, yes, if you happen to know a locale whose timezone is the same as UTC/GMT, you can use that, but that's still hilariously unfriendly to the user.