The best rates and very easy to use. I am using their service for a one and a half year now, I send money every month to my family never had a big problem.
You have to verify your ID after the first transfer and when sending huge amounts, you have to provide documents, where this money came from. I was a bit confused when they asked these documents, I called their customer support and they explained that this is a normal procedure as they are regulated by FCA.
Very good customer support! If you have any problems, or you don't understand something, just call them.