Chevrolet Spark knock sensor replacement

Since writing the review below and only rating Fixter at 2 stars, I have had a call back from an excellent customer services rep who had looked into my complaints, upheld them and addressed them. They have reimbursed me for the MOT and apologised for their lack of initial response. I hope this learning will improve the service for the future. Thank you to Stadia for her excellent work. I booked with Fixter after reading positive reviews but unfortunately my experience was not so good. The car was dropped back before the agreed time, and, despite someone being at home, they just put the keys through the door, so I could not communicate with them. It was returned filthy after I had had l it washed the day before and was literally sparkling when picked up. There was no MOT certificate with it and so I called to ask for one. I was told that they weren't given out any more which is not true as my husband had one the week before. It takes 5 days to update online so I had no proof my car had an in date MOT during that time. The customer service personnel said they would get back to me with feedback from the garage but never did. I then followed up with an email and never had a reply. I feel ignored.