Peugeot boxer motorhome electrical issue

Don’t know if this is the right place to discuss this but we have a fault with our van. After switching the engine off, the cab lights flicker on and off, the radio switches back on and off again and the side lights flash a few times. At first it only continued for a couple of minutes but now it does it constantly and has started to drain the battery. We have it booked in for a garage to look at it but that’s not until July. Was wondering if anyone out there has any ideas that might help before then

thanks in anticipation 

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