My own fault hair is "ginger"

You could always use a semi-permanent ash brown color to tone down your red.  What color is your natural hair color, I know you mentioned that it is now grayish, but what other color?  And, don't forget that this color will fade in about one week, and reds overall, have the quickest fade time.  So, don't be freaked out that you will be this bright red color for months on end.  That won't happen. 

Thanks both for your advice. You're quite right too - even today (6 days post treatment and many shampoos later) the color looks less brassy and I've had quite a few compliments so I'll stick with it for now. I'm a bit shocked that the stylist let me leave the salon like that, but on the other hand she's given me the best cut I've had in ages, so I'll probably go back there. Any thoughts as to how I can avoid a repetition of that tricky first week when I get the roots done next?  (Btw my hair is probably mouse with grey - I've been coloring it for so long I can't be sure.)