Salary transparency is something our industry doesn't always do well, so rates cards like this are very useful, especially for junior artists negotiating a salary for a new role, trying to get a realistic idea of what they can expect to earn.
Note that much depends where you live in the UK. The difference in the cost of living between London/the South East and the rest of the UK is significant. If you're further away from London, your expenses are usually lower, but salaries also tend to be lower.
So whether these are good rates really depends a lot on your location. In addition rates are, of course, lower for junior roles, for folks looking to break into the industry for the first time.