Steve
If I may share some thoughts from "across the pond":
As you've been advised, the first thing is to make sure the customer understands the limits of what can be done on something that has been terribly abused. I always check carefully for delamination on these items, as they seem to be learning how to make them cheaper each year.
You mentioned cold water in your extraction step. I don't think you need to be concerned with using hot water, within limits. You'll find you can more readily release oily soils from synthetic fiber fabrics with hot water than with cold.
These are the limitations that I use when it comes to heat:
1. Be careful with natural fiber fabrics. Some folk over here want to use boiling hot water on everything, but I see too many color bleeding and fading problems related to excessive heat on natural fiber fabrics.
2. Be careful with synthetic velvet fabrics. Depending on the type of tool being used, I am seeing more damage claims caused because of permanent texture distortion from high heat on synthetic fiber fabrics than I do any other type of upholstery claim.
I haven't seen heat cause distortion on faux suede (sometimes called microfibers over here) , though if you wish to stay on the safe side, you can still use very warm water rather than cold.
The only other damage issue (outside of making existing delamination worse or more evident) is marks from the edges of some cleaning tools. Using a tool with smooth or rounded edges rather than flat metal edges seems to minimize this risk.