Poor service from Hyundai Hatfield

My IX 35 when in to Hyundai Hatfield three weeks ago for a noise in the engine. Apart from the fact that the workshop took a whole week to let me know what the problem was and quoted me what I found to be an exorbitant amount, I agreed and they went ahead with the repairs. I heard nothing further and when I followed up, I was told that on their test drive, after the repairs they did, they broke down on the high way. They then informed me that there were now several other issues with the engine and the quotation for repairs now exceeds the value of the vehicle! My question is: How did they not notice the so called 'other' issues when they opened the engine? Or did they cause the other issues through poor workmanship? I have requested a technical report, which is not forthcoming. I get no feedback, I have to phone two or three times a week to find out what is happening. This service is unacceptable!