I have a ford mondeo Zetec business edition. First the alarm had started going off at random intervals. Then Saturday we went out, car showed no signs of any issues, then engine malfunction showed up on the car dash, ABS, traction control, air bag light all came on, car seemed to lose power in lower gears, then engine light came on. Car was still driving & the lights kept going on & off. Cars now in a ford garage, they said it's the body control unit & fault caused by water ingress. Due to condensation in the car apparently, therefore were not covered by our warrenty & they want £756 to replace it. We've found the part online for £66 is it something we could fit ourselves or does it need coding? 

That sounds like a cop out. If it is a 2016 car it should be covered by the manufacturers warranty. If the car is suffering from water ingress this is a manufacturing fault/issue and should also be sorted. Ive never heard of a 2016 car with such a problem before, or is this a different car to the one you have listed against your name?