Are they flat? I've always been under the impression that London rates are 25-50% more. Like at the moment the jobs I see advertised outside London are £350 a

Are they flat? I've always been under the impression that London rates are 25-50% more. Like at the moment the jobs I see advertised outside London are £350 a day, inside £450-550 (outside IR35, seems people are adding 20% for inside IR35 contracts).