We have established chains of shops that have over 1/3 of their sales on line. If you are setting up a new shop, especially if has a nice new niche then you should consider online only before you go to the cost of getting premises. Online is a great way of trialling your offering, and @UK PLC have started lots of pure online businesses over the years. The key is that you need to be prepared to market your business online, and this means fully describing everything that you sell.
If you have the cash to invest in premises, then you are still going to have to attract people to your new shop and @UK PLC can help a lot with the internet side of marketing your new business. We can also help sell to everyone that is not able to travel to your shop so that you can both sell online and via your shop.
You are going to be entering into a lot of commitments with your shop so it is best that you start life as a limited company, and the company signs the lease, purchases the stock and is responsible for paying your creditors.