ECU problem

[anderson]

I recently took my saxo 1.1 x reg to a garage because when i start my car even when its stone cold the temperature warning light comes on and the fan starts. They said i have a problem with my ECU and is gonna cost 300 quid to fix. The question is if i buy an ECU unit can i buy any ECU for a saxo 1.1 or do i have to have to buy the unit with the same number printed on my ECU unit

Thanks