Get you to a better headphone shop, bring some good music that you are very familiar with and compare the lot. A £20 headpiece will NOT sound like a £150 one if you are discriminate about your monitoring.
Listen for the hard to spot details, the stuff you lose when converting from wav to mp3 or like the meat of your finger hitting a string finished by the clack of a corner from your nail just clipping it.
A decent headphone will let you check a monitor mix for levels and pan-ing. Please stay clear of the "hi-fi" cans. Those are made to sound pleasant, not anywhere truthfull.
On your budget check out
-Beyerdynamic dt770 pro 80 ohms
-sennheiser hd 25 - 1
And their competition
One of these will take your music farther than any Beats, Skullcandy or other hyped up crap fashion brand.
Also, enjoy the search