If you have the time, soak the tree well and allow to drain for an hour before planting. While this is happening, dig a planting hole twice the diameter of the container and slightly deeper ...
The only thing you can do catastrophically wrong is to remove all the 2-year-old wood on apples, pears, and European plums.
You can grow fruit trees in pots in the UK ... pineapples, grapes, and stone fruits can all thrive in an indoor container garden. 'Melons and pineapples have a long history of being grown in ...