Electrical fault

Hi - really appreciate any help please.

A few weeks ago, after the first night in a while temperature had gone down to -6c, our Polo electrics started playing up - main headlights going off, indicators not working, wipers moving but not returning to neutral and warnings coming up such as water coolant low, bonnet open when the bonnet wasn't open and the coolant wasn't low! 

Been to garage - computer lists a whole range of faults mainly all to do with communication to control unit - has been reset twice but still doing it intermittently. Cannot go through more than one day without it being a problem - very dangerous when the indicators stop working!

Garage suggest replacing the control unit - does anyone have any experience of this? I don't want to spend £600 plus and still not sort the problem

Many thanks,

Jon