The advantages of being a sole trader are immense not lease because the owner has full control over the business for daily operations as well as how large they wish to grow it. It's easy to set yourself up as you only need to declare to yourself you are going to be a business but also have to inform the Inland Revenue you are self employed within 3 months of starting the business.
A sole trader does not need to complete many of the forms and accounting information that limited companies need to produce although accounts should be developed when preparing for your annual self assessment tax return where you declare your annual profits and tax liability.
As there are no staff on hand the owner also takes all of the profits made by the business and all financial information is kept private (whereas limited companies need to file accounts each year at companies house). You don't need to register a company either and can be known as almost anything and most people have businesses that are "trading as".
Decision making is also fast as it's just the owner who decides where the business is heading and whether or not to undertake any work and where and when they will work. They are generally closer to their customers and offer a more personalised approach and improved customer service as they are the person each customer has contact with.
Accountants generally charge less for company accounts and advice because there is less work to undertake. You just need to complete a profit and loss account rather than a balance sheet and cash flow (although it's worth preparing these last 2 on a regular basis to manage your business).