Hi kevin,
I have used the leather recolouring stuff from Furniture Clinic -
https://www.furnitureclinic.co.uk/Leather_Colourant_Kit and am happy with the results.
I used a 'standard' black colour as it was when i was fitting the Honda S2000 seats - so can't comment on the colour match for the Lotus seats - they do an 'exact matching' service (at a slight price premium), or have a selection of greys in their range.
I also used it on my centre console, door cards and A pillar trims and it hasn't worn away from any surface (yet!) - 4 years on.
The only comment I would make is that you may end up needing extra 'top coat' finisher - I added a couple of extra coats for the hell of it..... but if it's just for the seats then you may not need extra. (because I was doing other stuff as well, i also bought extra colour).
The kit they supply includes an airbrush and propellant can(s) - which is pretty rubbish to be honest. I already have a compressor and small 'touch-up' spraygun, and found it was easily the best way to do the job. If you already have them, it is possibly better value to just buy the colour & sealer/finisher from them, then use Acetone for the prep work with a scouring pad to clean it all up.