I've always fancied a fishmonger would do well on Union Rd. All those good catholics in Ossy wanting fresh fish on friday.
But what you also want to consider is using a shop as a front but finding something that is specialist on the internet for mail order. A good example is the second hand book shop - they actually do the majority of their business online but if you need a storage place for books you might as well have them in a shop so you get some passing trade as well.
That way you're not reliant on business in Ossy, or even within 5miles for that matter.