Language: The English language would likely be very different, as it would not have been influenced by Latin. It is possible that the Celtic languages would still be more widely spoken in Britain.
Government: The British government might be more decentralized, as the Roman Empire introduced a centralized system of government to Britain. It is possible that Britain would be a collection of smaller, independent kingdoms or tribes.
Religion: The dominant religion in Britain might not be Christianity, as the Romans were responsible for introducing Christianity to the island. It is possible that Britain would be a pagan country, or that there would be a greater variety of religions practiced.
Architecture: The architecture of Britain would likely be different, as the Romans introduced many new architectural styles to the island. It is possible that Britain would have more of a Celtic or Germanic architectural style.
Economy: The British economy would likely be less developed, as the Romans introduced many new technologies and economic practices to the island. It is possible that Britain would be a less industrialized country, with a more agrarian economy.
Culture: The British culture would likely be different, as the Romans introduced many new customs and traditions to the island. It is possible that Britain would have a more Celtic or Germanic culture.
Overall, it is impossible to say with any certainty what Britain would be like today if the Romans had never invaded. However, it is possible to speculate on some of the potential differences, and these differences could be significant.