Hey guys, not sure where the right place is to post this but I’m looking for some help and was wondering if anyone can’t help me at all?

I have a 63 plate focus. Last Friday it broke down. After being jump started, it started back up fine.
Broke down again yesterday morning which ended up with AA coming out and jumping it again. He couldn’t find any faults either on the car or with the battery, but explained something appears to definitely be draining it.
Ford wanted to charge £127 an hour for a diagnostic check. I was advised by a mechanic from elsewhere that even if they did this, if the car is running, a fault wouldn’t show up, so the costs would just keep running up. 
The mechanic advised to disconnect the battery and see if it looses charge. The battery is holding its charge. It’s only when it’s reconnected that it the battery is draining.
There is literally everything turned off in the car.
Not sure if this helps but, I’ve only had the car myself 18 months and in that time the stop start has been intermittent and only worked for half of the period I have had the car.
Sorry it’s so long winded, just wanted to give you the best idea of the situation. 
Any help would be appreciated.
Thanks, Luke.

You need to do a parasitic draw test.

Get a multimeter, remove the negative terminal and put one lead on the battery terminal and the other lead on the negative cable. Set your multimeter to amps and check how much current you have. My guess is you'll have a draw above 200mA if your battery keeps going flat.

Start removing fuses 1 by 1 till the current drops off, then you've identified the circuit at fault.

When you do the test, make sure the doors are locked, all lights etc. are switched off and you've left the car for half an hour ish. You'll get a false reading if you don't, as some of the modules will be awake and drawing current.