In response to your planning query, if the retail unit was previously used as a shop (even if it sold goods which were non-food) then you are entitled to use it as a shop again, without the requirement to seek planning permission.
A shop is defined in the Planning and Development Regulations as follows:-
‘a structure used for any or all of the following purposes, where the sale, display or service is principally to visiting members of the public-
(a) for the retail sale of goods,
(b) as a post office,
(c) for the sale of tickets or as a travel agency,
(d) for the sale of sandwiches or other food or of wine for consumption off the premises, where the sale of such food or wine is subsidiary to the main retail use,
(e) for hairdressing,
(f) for the display of goods for sale,
(g) for the hiring out of domestic or personal goods or articles,
(h) as a launderette or dry cleaners,
(i) for the reception of goods to be washed, cleaned or repaired;
but does not include any use associated with the provision of funeral services or as a funeral home, or as a hotel, a restaurant or a public house, or for the sale of hot food for the consumption off the premises, except under (d) above.
Basically, a change in use between any of the retail uses listed above would be considered exempt development under class 1 of the Planning and Development Regulations and therefore planning permission would not be required. So you should be able to set up a shop to display and sell your goods without having to obtain planning permission, if the retail unit was previously used for any of the above retail uses.
However, should you wish to sell hot food for consumption off the premises then planning permission for a change of use would be required unless it is ‘for the sale of sandwiches or other food or of wine for consumption off the premises, where the sale of such food or wine is subsidiary to the main retail use’.