Hi householders have permitted development this allows you to alter and/or extend if your proposal meets the set out criterion but this will be for the residential use of the dwelling house and not for business use. If your shed is existing you could apply for a change of use application. Check with your council what there advice on home working is. They will consider if the commercial use exceeds the existing residential use, roads in terms of increased vehicular traffic and parking availability, environmental health in terms of noise disturbance, potential smells, and the privacy and amenity of your neighbours- comings and goings of customers notice disturbance, will the building result in loss of light to the neighbouring properties and the amenity of your neighbours. Speak to your council and get a reputable architect/ agent who can advise and is familiar with the planning policy of your local area.