Are you a solo cleaner? If so, there is a finite amount of time available for you to sell. You don't have to be all things to all people.
Call around and check local rates. Set your rates to the high end of the scale. Then, do all in your power to make sure your service is actually better than the others. Present yourself well, be confident, and take what you do seriously. There are a lot of people out there desperate for a good cleaner they can trust. Clean well, be trustworthy, and show up/do what you say you will do. Dependability and trustworthiness are probably the biggest factors in what makes a cleaner worth more money. Being able to clean well, while important, is honestly less important than the first two.
Don't be afraid to demand more money. Sure, some people will say you want too much, but you don't need to appeal to everybody. Just the people who will value what you do.
Look at it this way: you can clean 10 hours for £15 an hour, or 15 hours for £10 an hour. I clean maybe 15-20 hours a week and I bring home about £300 gross from that. I started my business in January and my schedule is more than half full. I will be turning away work in a fairly short time. I think most independent cleaners are booked up by the end of their first year.
