When storing sandwiches in the fridge they share the same temperature as the rest of your food in the refrigerator.
So what temperature is required for storing sandwiches? You should keep your fridge at 40° F (4° C).
But bare in mind the ‘crisper’ draws tend to be of a much lower temperature, so don’t store any thing in these doors other than vegetables.
To verify the 40° F (4° C) recommendation, you can look to the UK Food Standards Agency to confirm any doubts.