Electrical Fault

Okay so started the car up earlier and everything is fine except it is saying 'electrical fault' and sometimes check auto lights. All exterior lights work fine however my radio will not turn on and the centre console where the time is normally displayed is also off, all interior lights will not turn on either. Any ideas?
 
Cars been to renault, paid £70 for diagnostics for them to tell me my UCH computer unit has failed/blown... £520 for that to be replaced. Then they kept my car for further tests to prevent the re recurrence of the fault, to which they concluded one of my interior LED (bought from Carbonfanatics?) has a short circuit which cause my computer to blow.
 
Cars been to renault, paid £70 for diagnostics for them to tell me my UCH computer unit has failed/blown... £520 for that to be replaced. Then they kept my car for further tests to prevent the re recurrence of the fault, to which they concluded one of my interior LED (bought from Carbonfanatics?) has a short circuit which cause my computer to blow.
I thought LED bulbs only worked in one direction so not sure how they could cause a short circuit if they are fitted incorrectly surely they just wouldn't work ?