you probably have a Dicksonia which is the most commonly found tree fern in the UK. It is possible for some varieties to produce side shoots from lower down the trunk but the most common type, Dicksonia antarctica wont do this as all the new growth is at the top. If it looks odd then just remove it.
The top will need protecting from the frost. When the fronds die back in the Autumn, fold them back into the centre and cover the top with plenty of newspaper and put a blanket over it. Uncover in the spring, remove the old fronds and some nice new ones wil appear.