You will all hate this next thought. The RAF has been slow, very slow, to accept contractors. Believe me thay can do a good job IF they are allowed to. The US Army knows how to use them. They can do things fast, efficiently and at a reasonable cost. I know. I spent 5 years post RAF contracting to the US military.
US contractors often see their role as a patriotic duty. Many (not all, but many) UK contractors see it as a way to do very little other than fleece the MOD