Beth's Jaguar X-Type changes specification throughout series 1. The Interior often changes from an early car to a later car throughout the the series. Notably the design of the front seat head restraints change design and the steering wheel changes from an all leather rim to a maple wood rim which also features a completely different design of wheel centre.
Casima discovered that they have been patented. Even if this was possible, the patent would end after 15 years like all patents in biology/chemistry. Since they are all over 15 years old, they are also patent free.