It may not add anything to the value of the car second hand, similar to how earlier cars with Ray's aren't really any more expensive than those with the standard 18's and those with the £600 optional Alezan leather are possibly even a little cheaper, but if I was still in the market and came across a GT with some of those options and a standard GT, both in similar condition/mileage/price, i'd definitely opt for the one with the sat nav/rays/alezan.
So, whereas it may not add value, it is certainly a selling point, of course Alezan is up to taste, but I want it