With how the law is written, if you think anyone might ever make a mistake (likely), think the government might ever bother going through the hassle of enforcing it (probably less likely if you’re not running a big website), and don’t have loads of spare money to pay huge fines with or to pay an age verification service with (likely), then blocking the UK is the only way to be compliant. It doesn’t require a technicality. The law just doesn’t have any leeway for honest minor mistakes or small hobbyist websites.