We have purchased a small piece of land in an industrial area of town. The only other food merchants are food trucks that come around with sausage sandwiches and other basic street food you'd find in the UK.
What is the daytime working population of the area you'll open up in? Most of your clientele will be people who work or live very close by.
I'd start by identifying the size of the market near you and then estimating how many of those people will choose you over your competitors. If you're offering something totally new and different for this area and demand is high, you shouldn't have much trouble getting people through your door.
With regards to your cost analysis - with any food business, the cost of food is typically about 30-33% of the price you sell it for. Staff often add another 30% and operational expenses, another 30%. You can use this benchmark to set your pricing and then monitor and evaluate as you go.
I have years of experience working with food start-ups on business plans, financials and market research and would be happy to have a call with you.