But wait a moment. Everywhere you turn, you're advised to get professional help to edit your book, to proof-read it and – in particular – for a cover. Even if you're an ace with Adobe InDesign, don't trust yourself with your own cover.
In each case you get what you pay for. So for a quality result, you might end up spending hundreds of pounds. You'll not get that back selling books tucked away on the internet for 99¢ per download. So oddly enough, the best way to get your money back is to print a few copies, using the same cover and so on, because you can make a greater unit profit on each sale. You'll get your money back quicker in print; you'll make money quicker selling ebooks. I honestly think you need both, you're wasting your time just publishing ebooks.