Feasibility study for coffee/tea shop

I want to open a tea coffee shop with the idea of it becoming a chain, along the lines of Pret a Manger, Costa, but with a subtle Asian twist and a larger tea selection, and an emphasis on ice cream also. I have an investor who is keen to invest but wants the feasibility study. I know for a fact that approximately 45% of the UK adult population visit a coffee shop every day. Shop will be in central London Zone 1 with high footfall. It is a completely new start up venture, my background is selling property, though my passion is cooking, and tea. We will need to lease an A3 unit, pay premimum if it's in Zone 1, set up the unit as we want. Everything needs to be considered, design, stock, logo, staffing, supplies, wages, management. It is not a hard sell but the figures need to add up and be realistic, he will definitely be getting a second and third opinion so it needs to be something a bank manager can look at and an accountant with positive feedback. Need it asap, within a week or so.