Leather is a problem I have learned in the last 2 years
Right Frost Restoration do a spray for small area ware. I tried it to re colour leather door cards not brilliant but quite acceptable i supose.
I had two seats recoverd by an excellent outfit in Liverpool errrr at a cost! PM me if you want to know mind job is fantastic
However if you want have a go with the spray i have 2 full cans of black left over cost me £28
I can show you the results of the spray
Let me know if your interested