sick 2003 hdi after new alternator

[goa55]

can anyone help my 2003 63k berlingo is a bit sick, it had a new alternator recently and a new battery, the old alternater was overcharging a lot, now the car runs etc but the battery light come on after a few minutes and today the whole car cut out and would not restart, after a few mins rest it re started fine... is the ecu on the way out maybe damaged with the overcharging ??

any idea what going on ??