Had an engine management fault called RAC. Patrolmen arrived immediately did a battery test and stated we needed a new battery cost £385.00. When challenged regarding the diagnostics then proceeded to check, than stated it was a rear wheel sensor. I said it's not the battery then? Oh you still need a battery and pulled out a drawer with numerous batteries. Needless to say, we declined.
He directed us to a local garage who quoted us £400 for parts, we declined. Then went to a Mercedes specialist. Full diagnostic. Problem rectified £135.00