Well the British Empire is actually covering a looong time period so I wouldn’t say it’s inappropriate itself, considering you can still see bits of British Empire!England in canon.
But I just think it’s important to keep the hetalia spirit in mind while answering. Like, don’t idealize the bad parts, don’t forget them but don’t focus too much on them either. Since Hetalia is mainly about trivia, and barely-or-not-at-all talking about touchy topics, I’d advice to probably only imply the bad parts yet clearly enough to understand that some deep shit is happening.
And about the said bad parts of history, don’t demonize the character either, think about why he would act the way he does and even if his reasons are not valid for everybody they completely are for him.
The tricky thing is to find a well balanced way to show that bad things are happening, that England would be 100% guilty of them, but that he would totally have his reasons to do them, even if from another point of view the said reasons are 524365% not valid. And all of this while not being interpreted as “finding excuses for the perpetrator of such bad things”.