Fairly heavy battery drain

I know battery drain has been covered many times but as this is fairly heavy, I thought someone may have a clue where I can look.

New battery drains overnight - completely dead. I have test equipment as my hobby is electronics but I'm completely new to car electrics. Battery drain is a hefty 5.8 amps or around 70 watts. Sometrhing should be getting warm but I can't find it. I had the car run through a diagnostic test by computer just before Christmas as things like that are very cheap...

Fairly heavy battery drain