The racial history of the UK is pretty bad historically, and over the last 60 years, we’ve had our share of riots, police brutality, and marginalization. But, in the last 100 years at least, there’s not been any notable organized, let alone official, obstruction of people voting based on their perceived race. Like the Irish poster above said.
I have never had to wait more than 15 minutes to vote or walk more than 15 minutes to a polling station. I’ve never had to show ID, and I’ve even been able to vote when I have forgotten my polling card.