Self-publishing or commercial publication? It depends on what you’re after.
When a novel is published by a commercial UK publisher, sales of 2,000 or so copies are considered poor-to-reasonable. In self-publishing, sales of 200 copies or so is way above average.
If you want your work to be read, to earn money for the privilege, and to concentrate on writing rather than publicity and sales, then commercial publishing is the way to go. You’ll be able to concentrate on your work, be given specialist help at every stage of the process, and will probably earn a reasonable-to-small amount. However, as most people are just not good enough writers it’s likely to be very difficult for you to get an offer of publication; you’ll have loads of rejections (which can be heartbreaking); and might not even be consulted about things like jacket design and cover blurb.
If you just want to be published, then self-publishing is fine. You’ll get the instant gratification of your book in your hands, and it will be produced exactly as you want it to be—so long as you can afford it. You'll probably lose money overall as printing, design and distribution all cost, and you’re unlikely to make that money back through your sales. Your life will not be rejection-free: you’ll be responsible for selling your books, and few bookshops take self-published titles. And you’ll have to be happy spending your time marketing and selling your first book rather than writing your next, as that’s what you’ll have to do if you want to sell anything like 200 copies.