Aren't leather seats and steering wheels sealed? And I'm pretty sure the sides of my TI seats are actually plastic. I was at the Rolls Royce leather shop a couple of years back and was told nearly all seats are sealed rather than oiled like old Jags etc. there are some Rolls Royce leathers that would need balm, but apparently these leather cleaners and conditioners are a waste of money on modern interiors.
I've used Gliptone, Autoglym and others and I've always felt it was just my hand or cloth that was getting conditioned. Smelt nice though. I've just been using mild soapy water for a about 4 years, takes the grease sheen off the leather, dulls it back down. If everything is sealed, it's just surface muck/grease and fairy is good for grease. Keeps my steering wheel matt too.
GT 3.2 V6 - Q2, KONI FSD & EIBACH PROKIT, GTA REMAP, MICHELLIN PS3's, BMC CDA
159 SW 2.4JTDM TI - ALFATUNED, WIZARD BACK BOXES, KW V3 COILOVERS, NOKIAN WR A3/MICHELLIN PS3, PCA DYNAMICS ALIGNMENT.