A deep clean will ensure that the conditions inside the shop are sanitary. Even if this doesn’t appear necessary, a closed store is easier to clean than an active one. A whole room fogging disinfectant will deal with an entire indoor environment for a few hundred pounds.
Pests can make their home in vacant premises. Look for evidence of vermin before re-opening. Beehives, rat-droppings and other markers might indicate a problem. By the same token, Legionella bacteria can thrive in stagnant water. Your water supply should be checked by an appropriate company before the stagnant water is drained. The Health and Safety Executive provides exhaustive information on the subject.