May i present you my cheap bandaid fix..
First of all, going on a few assumptions here, first is that the mechatronic unit has been leaking slowly since day 1 of replacement, then that the garage cowboys used tiger seal instead of the real gasket that should be used. I'm assuming that because that's exactly what happened to mine.
Now, if you can remove the battery, battery tray and pull the air filter box to the side enough, you'll see the breather black cap on the mechatronic. Assorted torx bits and set of sockets with extension bar needed. Once you find the right torx and hex socket they're good for the whole job. Oh and a set of pliers. That cap comes off harder than expected
My unit started throwing faults at around 600ml (measured left in unit) out of 1L, so 400ml of "MVCHF" comma brand central hydraulic oil from halfords will set you good. It's £10 or so, chf11s spec so matches oem.
The little valve is around 8-10mm outside diameter and 5mm inside diameter, syringe or funnel with a hose should work just fine to top it back up. If you want to do it the proper way, assuming it's a 1.2tsi, starter motor needs to come off, so don't bother, just use the breather hole and slowly pour in what you need, and if it stops shake the hose to force a bubble out.
I'm doing this for the past year and a half and 50.000 miles. Once topped up it's trouble free for half a year or more, depending on gasket gods mood that season