We recommend the Locks4Vans Replock replacement driver’s door barrel for all Transit owners, start Googling the subject and you will find loads of videos of how to outwit the OEM central locking on MK7 Transits (simple lock pick, available online), MK8 Transits and Transit Customs (pair of mole grips will do the trick here).
The L4V Replock replaces the OEM door barrel with an unpickable version and comes with a steel bezel that sits around the cylinder to help protect against screwdriver attacks.
This is probably the minimum security upgrade that Transit owners need to consider, and can be keyed to match the cylinders on your existing Locks4Vans deadlocks and slamlocks for extra convenience.