Our new car has Black Leather seats, a few scuffs nothing serious. So I was wondering what is the best product to add colour treat and preserve

I use saddle soap to clean and nourish the leather. i can not help with scuffs.

have a look at meguires leather cream it should cut down the skuffs. also trick of the trade can be to use shoe scuff remover however dependant on where the skuff is.

I use Gliptone on both my cars with leather. It makes them really soft and the smell is great http://www.liquidleather.com/

i use croftgate i think its called off paul from seat surgeons

I use ArmorAll Leather Wipes. Very convenient and leave the seats looking really nice and feeling really soft.