Best advice? Get on GOOD working relationship with the EXPERIENCED parts manager at your local independent LR specialist.
They will be able to tell you genuine, OEM or aftermarket. They can tell you the source of the part in many instances.
Also an experienced parts manager will tell you when they will fit, a genuine, OEM or aftermarket part. OK they might be slightly more expensive then a online parts supplier BUT the advice from an experienced parts manager is worth a premium.
Last week at our local specialist we got various parts in and lined them up for comparison. We picked 2 out of 3 and the third was returned at no cost to us.
Get on GOOD working relationship with the EXPERIENCED parts manager at your local independent LR specialist. The local garage will not want to fit crap parts as they will just get a warranty claim which they want to avoid