I was searching for information about artists' hourly rates in the UK and discovered THIS amazing illustrated freelancer's guide from www.creativescotland.com. Personally, I found it incredibly useful for many things. It covers so many topics, such as tax payments for self-employed freelance artists, handling unpaid invoices, etc. It's the sort of information that is usually hard to find. The guide is completely free, and I highly recommend to check it out.