Vauxhall Signum battery warning temp warning and engine electronics lights on

hi all im hoping someone out there will be able to help.I have just purchased this vehicle 2nd hand. After test driving it for 30 mins both on open and residential roads all seemed fine. I then drove it on a motorway for 2 hours doing approxiametley 60-70 and 90 miles (also half an hour compulsorary straffic jam at the dartford crosiing. Everything was fine. Ive just got into the vehicle 3 hours later and driven it 200 yards and the warning lights came on. i pulled over switched of the ignition waited 5 mins and turned back on, all was clear. this happened 3 more times in 5 mins, the last time the temp rocketed up and the warning light flashed on and off like a xmas tree light. I phoned the person i bought it from and got the "it never happened to me" answer. before i go blind to a main dealer and prepare myself to be ..well.. is there anybody out there that has had or heard of a simular problem and can let me know what im letting myself infor? If i thought the car would do the 90 miles im tempted to drive it back and ask for my money back, however im completly in the dark with this and am hoping its nothing serious...sigh.. please if you can help id really appreciate your input..thanking you in anticipation...