There is no government advice that says we must not go fishing. Below is the only semi official advice that I have found.
Common sense says that social distancing or even isolation on the bank of a river or lake tens, if not hundreds, of metres from the nearest person whilst getting exercise, fresh air and relaxation, must be most beneficial.
With the river Wye in close season that leaves the Monnow and Trothy for the occasional trout, or our lakes. Carp have been caught last week from Brick Kiln Lake and rudd, roach and perch on the others although at 10 degrees the water still seems to be too cold for our tench.
So get fishing and keep healthy.