Warranty fixes

I have received two letters dated May and December regarding the battery insulating mat. My dealer cannot help, so I sent an e-mail to Skoda Customer Services asking why this 'safety critical' issue was taking so long to fix. I received a reply stating that the following three items are issues to be fixed: the insulating mat, S-Update Gateway control unit software and OCU control unit. Our car is already booked in on February 8th for a software update to address the 12-volt battery problem (discharged twice overnight) but what is the OCU control unit and what does it control? Skoda UK will put me in touch with a 'Battery Competence Centre' to arrange for the insulating mat to be fitted and I've e-mailed the dealer to ask whether they can replace the OCU control unit at the same time as the software update. I'll post an update once these issues have been seen to.