Can I add my 2 cents?
Firstly, mobile stylists don't need to use cheap stuff. It costs approx £3 more for a tube of good stuff, and that would do a full head on a client with short hair.
Do the maths - £20 full head colour, cheap crappy brand. £23 full head colour, good and well supported known brand. One delivers results far superior to the other.
Secondly, you can't compare any products by simply looking at the ingredients lists and stating that similar ingredients = similar results. Has anyone actually tried to compare Aunt Bessie's Homestyle Chips to Asda Farmfoods in taste and quality? Both have just 2 ingredients - potatoes and oil. Similarly, every cake you can buy contains flour, eggs, milk and sugar. Using the 'ingredients comparison' method, I guess that should mean a Tesco Value sponge would be equally as adequate and tasty for your wedding as any Marks & Spencer special order? Think about it. It's how the ingredients are sourced, blended and prepared that makes the difference, not the ingredients list themselves. Hopefully the above food analogies go someway to demonstrating that point!
Finally, Si...you are contradicting yourself and I think that's what makes it so confusing. You say you are dismayed by the lack of education received by younger hairdressers, but then make posts pointing out that (in your opinion) generic peroxide and supermarket shampoo are just as good (if not better) than the professional salon brands. Is this your intention and true belief, or do you think that great results start with great products? I am confused?