Should I rent a car or just take the train within UK?

Hi! I will be going to UK this week and I will have to travel a bit around the country. I am not sure which mean of transport to use. Can someone tell me if, in their experience, it us better to rent a car, or to go through UK by train? I will appreciate any help. Thanks in advance.

I have tried both means of transportation. Both are satisfactory to me, but if you are not experienced with roads in UK (because of the opposite side of the wheel), it can be a major problem, at least in the beginning. Now, train is an excellent alternative. They are very fast (up to 200 km/h), really reliable and never late. Also, they do not stuck in completely unbearable traffic jams. However, if making your plan according to departures and arrivals presents you a problem, and you would like to depend entirely on yourself, come several days earlier, rent a car, and try adjusting to the new way of driving.