ECU failure

I have a 2014 BMW F30 320d auto that has performed flawlessly for the past 66k miles. However, on arriving at work last week the car seemed to have a fit. Initially I lost powered steering, followed by a warning on the idrive titled 'steering', continue journey at moderate speed, increased steering effort required, have the problem checked by service. Immediately after that I got a second warning on the idrive, 'restraint system' function of airbags and belt force limiters fault, ensure your seatbelt remains fastened and have the problem checked by service. My a/c then stopped blowing cold and my speedometer was no longer recording my speed. My trip/odometer were also not recording anything, and auto start/stop was illuminated as it does before the engine has warmed up. I parked the car and continued with my day. When I returned to the car later that day and turned on the ignition, none of the aforementioned faults were visible, the power steering worked fine, the speedometer worked fine and the odometer worked fine. It was like it had never happened. Midway through my drive home however, and quite abruptly, whilst I was in cruise, all of the faults came back alongside a cruise control failure on the idrive! I booked the car in to d*ck Lovett BMW yesterday and unsurprisingly they were unable to replicate the issue on a test drive, but they did identify the fault coding from the previous occasions. They cleared the faults and since they couldn't replicate the problem suggested it may have rectified itself. 20 mins after leaving the dealer it happened again. The dealer is suggesting it is a faulty IMU and DDU, and that if it continues it will require both units replacing, at a cost of £3200! He said he had never seen a failure of the DDU and IMU before, and given my car has full service history and is only at 66k he would offer some form of goodwill to reduce the cost. Has anybody ever heard of a relatively young well looked after BMW having a complete failure of its onboard computers? The car continues to drive when with no issu when these faults occur other than the loss of power steering and a/c. Any advice would be much appreciated, I had considered selling the car soon but now I cant unless I fork out 3k! :( (My drive to work today was flawless but last night the dashboard was illuminated like a Christmas tree) Thanks guys