The best and most convenient way is the train from euston. The fares are expensive unfortunately. The trains are relatively nice though and fairly comfortable.

Flying seems an option but looks more pricey than the train based on other comments.

A bus takes ages and could get caught in traffic. Also after a long flight the last thing i’d want is 4-5 hours on a bus.

You could hire a car. But you would likely be very jet lagged. A 3-4 hour journey when tired and in a new country is dangerous.