Cannot fix but demand payment

These are the most ********* and *********** people you will ever come across. I took my vehicle to them with a severe misfire. Since I am technically minded I have diagnosed the most common causes and after determining that none of these were the cause I took it to the 'experts'. They insisted on booking it in for an 'inspection'. Two days later their 'mechanic' phoned to tell me he found the cause - Low compression. I requested a report that I never got. I went to their premises and showed him by means of elimination that it is not the cause. He agreed and promised to investigate further. I went back 3 days later to be told that sensors were sent in for testing. 2 days later I was told that these were fine and there MIGHT be an electrical issue, I have to take the car to an auto electrician. Again I requested a report that I never got. To get my car back I have to pay the inspection fee which tells me nothing, only that they cannot fix the vehicle. Use your backyard mechanic, you are much better of. These people have no qualification and no s****s to fix anything AND they are NOT the cheapest either.