Okay, so I have quite light brown hair and wanted to go a little lighter so I used sun in and now it's turned brassy and orange and now my roots are showing and I look awful!! Any ideas?

Other than letting it grow out the only other solution is coloring it.

Will try that! Thx

Years ago I used Sun-In and the same thing happened... brassy orangey color :( To correct it I used a demi-permanent color in a dark ash blond (Goldwell Colorance #6A). Ashy tones counteract the orange tones so you end up with a more neutral tone. Since you said you wanted to go lighter, you could look at a lighter shade with an ash base. Hope this helps :)