look at the furniture clinic, they have a great DIY kit to use, or LTT leather care and Dr. Leather to maintain.
They are the 3 companies I trust and use for mine.
Not many people realise that modern leather is much like car bodywork... i.e. it's actually painted... so fixing stuff like that is pretty easy.
And the above is a reason why all these conditioners etc are a real waste of time and money...