2004 Other MG Models

Hello, I brought beautiful 04 plate MG ZT, 99.000 miles on clock. After approx 1000 miles trouble free drivinge, the car was admitted to local garage with loss of gears problem, the mechanic charged me  £350 for new clutch job, on collection steering allignment was off and the gear nob was on passenger seat so could not safely drive away, so had to return later that afternoon to finally collect. After 5 mins of driving the overheating light illuminated, the car was re-admitted to same garage and I was charged  £80 for a new sensor for thermostat. Within 10 minutes driving, approx 1 mile of collecting car for third time, the head gasket blows, I was charged a further 550 for new gasket job. Total time taken 3 weeks and 2 miles driving since initial clutch repair!
5 months, and 1500 miles later the engine head needs replacing again, and vehicle has further damage to the engine as result of gasket failure. HELP, what can I do? Where do I stand with regards previous mechanic repairs, he's trying to blame me now that further damage has been done to car as result of failed gasket that he supposidly fixed, plus charging me for a new gasket - surely this cannot be right? Any advise would be gratefully appreciated, thankyou.