I have Autoglym leather clean and balm, as per their website clean and treat leather twice a year is sufficient. In hotter countries (which UK is not) apply more frequently, or if you have an accident like I had a few weeks ago with my cat, then treat the area as required.
Down to preference on what product you want to use. Swissvax, Auto Finesse, Autoglym... take your pick
Im slowly phasing out my Autoglym set and making switch to Auto Finesse but there some products I will continue to use like car glass polish.