That’s awesome if there is an EU standard. Do you know what it is?
Is there a EU-wide database?
I know we also have a countrywide standard and shared database.
The USA i’m not sure if the standard is the same, but they don’t have a shared “Tracking” database.
Have you scanned the cats chips? or do you have specific info on them?
If you have a PM3 RDV4 and one of the newer LF antennas ( Not the DT one ) But the one with the 134kHz switch,
Try scanning with that because it is LIKELY that freq. ( Probably FDX )
If not a “standard” 125kHz antenna with scan it fine also.
Rosco did some work around a solution and also found the expensive ones, let me try to find his thread /post…
Also, do yourself a favour; Get a dog ! 
Still agreat project by the way.
I just found this one, It should be a good starter for you