DD1 is 16 and is getting a camera (if I can actually find one). some Kate Moss perfume, a subscription to Glamour magazine, some books and a few 'bits' such as PJs, knickers, socks etc.
DD2 is 14 and is also 'indie.' She's getting a subscription to Kerrang as her main present (it is v expensive) plus a huge book about the filming of Harry Potter plus various 'bits' and some CDs.
I agree that staying away from clothes, bags etc is wise as it is so easy to get wrong. My dds wouldn't like anything from PB, Jack Wills, Hollister etc but would be v pleased with something from Urban Outfitters but even I wouldn't dare buy them clothes tbh. Even if I went to UO and bought something that looked like the sort of thing I'd think they'd like, it would inevitably be wrong!
For a 35 pound budget as a generic gift for a teenage girl I'd say something like:
straighteners or a hairdryer plus some really nice shampoo etc (Tony and Guy maybe?);
Urban Decay or Mac makeup - perhaps a black mascara, a black eyeliner and a neutral lip gloss which can be adapted to whatever her chosen 'look' is. You could also book her a makeover at wherever you buy the make up.
A huge box filled with hairspray, nail varnish remover, cotton wool pads, eye make up remover, bubble bath etc etc.
Cosy PJs, fluffy socks and an eye mask/hot water bottle with fluffy cover.
I can probably think of more ideas, if any of these sound on the right lines!