For cleaning, If the seats have not been redyed, Spray on some all purpose cleaner and wipe with a microfibre, if they are really dirty you can use a scrubbing brush no problem (as long as they've not been redyed) Dry off properly with a microfibre and then apply some leather conditioner.
I use Meguiars Mirror Bright Leather lotion, then sniff the seats!

I can also recommend the mirror bright detailing spray....both work very well Indeed AND smell amazing.
View: https://m.youtube.com/watch?v=XMjtqOi24_4
I really rate the Meguiars gear. I use it professionally for my detailing. Some traders i work for have Autoglym and tbh there's not one of their products I'd choose over a Meguiars equivalent.