I filed my first tax return this year online. It was rather easy. Like it has been said, all you need is a record of your income/expenses. The most annoying bit was getting HMRC's User Id and Password...what a nightmare. But once I got it I started looking for free alternatives because, as a designer, I get really bothered with the official site. Found one that was free, simple and nice with fast support. I'll be using the same site this year (this time sooner rather than later, i want to be done by May).
Don't fear taxes, guys. Fear audits