I used Gliptone from here : Car Leather Cleaner on the 147. I sent them a little sample from inside the map pocket but they send you the basic colour anyway and some tints to alter it. After 7 years I wore the bolster so was just patching that up. There's lots of options on Youtube too.
If that needs sprucing up, my tan leather is about ready for the bin. Tis mint!
I used Auto Glym leather cleaner and feed, together with a soft bristle brush + some cloths, to take out the grubby 100k nastiness in mine. Almost like new afterwards - you'd be surprised at how good most leather is, if it were cleaned.