Q.weeping willow tree problems
I have a new willow tree in my front garden. I planted it last year and it seems to do well. However, I’ve now noticed that the bottoms of each stem are sprouting new branches/catkins but there is no life at the top of the tree. I’ve had one before so I know the trees grows up and also wide, but this looks very strange, as there only seems to be life at the bottom of each branch.

It sounds as if your tree may have died and that the root stock has taken over and is growing.
The top of the plant was grafted unto a root stock standard in most cases with these ornamental Weeping Willow Trees.
You may want to contact the greenhouse or garden center, as most reputable sellers will guarantee a new planting for 1 year.
Here are some links with more information.
https://www.gardeningknowhow.com/ornamental/trees/willow/grow-a-willow-tree.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/can-grafted-trees-revert-to-their-root-stock.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-scratch-test.htm