Perhaps look up " garden gate sales of surplus produce " for a bit of info on how you stand
Doing it commercially as a market gardener might have several implications you need to comply with though . One thing that comes to mind is being registered and trained in the use of agricultural chemicals and the safety angle of it etc.
In my first marriage of nearly 40 yrs. ago :-
My 8 yr old daughter took all the surplus stuff like sweet heart cabbages cauli's , peas , carrots and salad stuff out our house garden round the housing estate & sold it for her pocket money .
That soon brought council down on us for a shop keeper had complained that she was an un licenced trader.
They told me about the garden gate sales permissions & also told me when it would not be considered as garden gate sales .. it's well worth a look to save your self grief most likely things will have changed slightly but I think that the rules will still be there.
One thing I do know that could cause you grief is a complaint by the county traffic /safety officer seeking to prevent you doing it because in their opinion your selling could cause a traffic hazard ( If you are on a busy road or on a bend etc. )