Go with this kit
Leather Masters Kit:
Strong cleaner
Vital Conditioner
Protection
Here is how it looks in an e39 m5.
The interior for this M5 was for lack of better words shot, dust everywhere and sun block all over the door panels and front leather seats. We cleaned up all the leather with Leather Master Rapid S and conditioned them with Leather Master Vital. All the plastic trim with cleaned up and protected with Einszett Cockpit.

After shots:

Door panels before Leather Master treatment:

After shot of the panel: