The first thing you need is YOUR idea - write down what it is you want to do, then list out what you need to do it.
High on the list will be £££££, and this requirement will always be more than the resources reasonably available to you (unless you are the son of a Duke etc.) To fix this gap you may well think "I'll pop down to my local bank, and they'll credit my account with a quick loan, I've seen all those adverts with smiling small business people/horses galloping over the plains". Don't waste your time unless you have freehold property to pledge as security. Most of us don't have this, so the solution is to trawl the venture capital/seed capital online markets. This will take aeons of time and frustration, but you will get your money in return for surrendering twice as much control over your business as you were prepared to.
Hint, if you can find any way to get started without funding, to demonstrate there is a market for pink spanners with white lace trimmings, this will really help the fund raising as you can point to --->> sales achieved with inadequate resources for 12 months, in which time you have learned xx, and refined the offering to target yy customers etc.......
Remember online markets like Ebay is cheaper than renting a 20,000ft shop/warehouse, so start small and scale up.
Would you like us to do your Business Plan? £5k upfront, and keep counting, so i suspect not.