Hmmmm,
for £70 you get get quite a few earphones,
The E2c from shure I find lacks in bass... If you have a wide genre preference then they'll be the worse headphones to get, however if you like classical/jazz/fusion with no prominent bassline then they're great. Shure are renouned for their sound isolation.
You can also purchase Etymotic's ER6's, I haven't tried these yet.
Sony MDR-NC11a or previous model MDR-NC10a, the first model is the latest and can be bought off Argos extra for £59.99, Sound quality is as good as ex71's when the noise cancellation is off, once it's flicked on the sound becomes strangely brighter. However the noise cancellation really works

, it clears out about 10db of sound.
The Sennheiser CX300 are also great headphones which offers a better sound quality.. more brighter than all sony's I've ever used, it also delivers a great bassline however it's isolation isn't as near as Shure E series, nor the Sony MDR-NC11a's.
Drx.