2010 Sri problems

[Addavies]

Hello,

recently purchased a 2010 Insignia Sri it’s been a dream to drive but Sunday morning my partner was driving down the motorway when there was a loss of power so he’s pulled over turned the car off and waited a few minutes before turning it back on when the car then showed a warning message “engine over heated stop” checked fluid levels and the coolant was bubbling, we called the rac got it recovered home. When it got home we’ve tried to start it and it cuts out the coolant has now gone the bottle is bone dry, plenty of oil and the oil cap is clean. So we filled the coolant back up and jumped it and got it ticking over but it sounds rough really lumpy which it didn’t previously. We have a friend who plugged in a Bluetooth diagnostic and no fault codes presented. 
 

any suggestions would be appreciated, I know getting a new battery is first on the list but I don’t think the battery would cause the engine to sound so different. 

[Vauxhall Owners Club]

I would not try running it any more as if the coolant has entered the combustion chambers then it could lead to melting the pistons or even hydraulic lock