Sometimes electrics can be a pig.

I'd guess in this situation it'll require a setup that can monitior the system over a prolonged period.

I think if I recall correctly Snap On had a problem diagnosis with battery draw that required one of the better diagnostic units to be plugged into the battery system for 24 hours in the garage.

I'll have a thunk and see if I can recall where I viewed it.

Anyway it's still a case of monitoring recorded data until a spike appears.

The first auto electrical company I took it to said they had gone through the procedure of 'pulling fuses' they also did diagnostic checks, Although they found and corrected some faults I wasn't aware of [I have the diagnostic readout]. The end result was they have said 'it still has a Small drain'. The recommendation was to take the car to a Ford Dealership, which in Hindsight I should have done first. They want £106 to look at it and whatever on top to try and fix the car. I have seen online even Ford garages unable to correct the fault.