...I just checked the England and Wales birth data, and there's not one single historical instance of it having been given to a baby as a first name. There is one kid in the whole country with Thatcher as a first name, and he was born in the last 20 years and has a very African surname. Like
Janan said, random surnames as first names haven't been used here until very recently; it's a borrowed American trend.
So yup, trendy. And lol yes, people would totally think you were Tories!