HazelT

Hi everyone, looking for some advice please. I own a 1.7 astra sxi and today my partner drove it to football and on the way back it completely died on him, he eventually got it started again but the car was making a strange "putt putt" noise and fumes where coming out of the exhaust, also the car wouldnt go above 25mph. After leaving the car on the driveway for an hour we tried to restart it and it started making a really loud knocking noise and was revving by itself without us touching the clutch, also large clouds of black smoke came out of the exhaust. Can someone please let me know what you think the problem is and if you think its worthwhile getting it fixed or too costly?? Thanks in advance Hazel and Kev