Idle and over heating problem

I've just brought a Renault Megane 1 2001 1.6L 16v When i was driving in the car the other day I was going really slow, the car would really over heat at one point on the dash it said "STOP" So we let the engine cool down and drove back on the motor way and it was fine at high speeds but i really am stuck and have no idea how to fix this issue with my car please help??!



Extra information relevant 85k Miles

Mot was in November.