Richard,
I'm somewhat surprised at your answer.
We use Renovate as our primary detergent for all our FDR work, but find it often fails on nicotine staining...
Unsmoke have fairly recently released their new nicotine range down under and we did our first job with it about 2 weeks ago. We had a protien fire in a tenanted property with three chain smokers... unfortunately both residues are yellow, and of coarse ALL staining of protien soot residue :?
We cleaned all areas with Renovate and most came up ok, but when cleaned again with the Unsmoke products, it did come a lot better.
I'm more talking about hard surfaces when you've raised it about fabric but worth mentioning.
What mixing ratio do you use?
Cheers, John