My viburnum minus leaves and flowers have turned brown, dry and wilted.
Could it be cause by a disease or fertiliser burn because I spread about a handful of Growmore granules around the roots in early March.
I'm not able to enlarge this image and can't really get a good look at the plant or any detail on the leaves.
Yes, over fertilizing a plant certainly can lead to burns or plant die off.
Leaf fungus issues or bacterial disease can also be an issue with a plant in the description you give. Clean up any dead plant material around the plant and dispose of.
Avoid overhead watering.
These links will help you determine if you have pests or disease and how to treat them.