1992 Honda Prelude Over heating then knocking

Drove car back from London, When we left the oil light came on so we added oil,the light syayed on despite adding more . We had to drive it back to Plymouth, It overheated after e few hundred mile . So put some water in let it cool down , but as we got into Plymouth car was overheating again. Its now knocking under V TEC cover,please tell me that ive not blown the engine!!!!,Is it possible that the tapping could be put right and the car will run again. or do you think we ve just wasted what we paid for it in London.Thank you for your help b sure 2 make donation on next visit,Mr Bryan Dustan