You have two or more days pre-or post-cruise to spend.
If the thought of navigating London is overwhelming, then proceed to Southampton which, besides being a busy university town, is also a great jumping off point for exploring attractions in nearby areas. That is in addition to the very local ones mentioned previously.
Take a day trip to the Isle of Wight, or the New Forest National Park. There are guided tours to Stonehenge. In nearby Winchester, there’s a wildlife zoo or visit an oceanarium in Portsmouth. If you love cars, put Beaulieu on the list – there are nearly three hundred vehicles on display at the National Car Museum! If you are a child at heart or travelling with children, there is even a Peppa Pig World! Going further afield, visit Windsor and enjoy an afternoon tea in the town before visiting the castle and park. The one of many advantages of vacationing in England (and many other European countries) is the distance between places you wish to see. Within reason you can pack a lot of activities into a day especially with the train system.