The below is true but I have been looking into this and I dont need
Planning Permission as its less than 1/2 size of property, more than 5
meters from house and not higher than 3 meters from highest point of
ground as the garden is split layer.

But what is the cubic volume of it, compared to the original house? Are
there previous extensions/conservatories etc. Is it in a conservation
area and were the permitted development rights withheld when the
property was built (many estate locations would be built with permitted
development withdrawn).

Christian.