Battery going flat overnight done a parasitic test found nothing also radio wont come on yet sat nav does any help much appreciated 

Morning Steven

There are a number of possibilities to check

1. Does the car go to sleep?

2. Battery age and condition. Even a new battery can fail as an example the OEM battery in the 4.6 died after 14 years I replaced it with an OEM same size same rating 9 months and issues Battery replaced 3 times under warranty before the issues stopped

3. Unplug the BM54 unit in the boot check the fuse in the Quadlock plug 

4. What use is the car getting? many of us are not doing decent journeys so the battery never gets recharged properly. I use a Ctek charger once a month 

5. Any other functions not working properly (eg Indicators not clicking but working, side lights staying on) could point to an LCM issue

Do you have a BMW Diagnostic reader? A scan will quite probably help locate the problem

Dave