At that price, these are an absolute steal!
£15.68 with NUS discount - I'll hopefully have them by Thursday. :D
I remember I bought mine for around $70 on Amazon then my friend mailed it to me (ended up about $80).
Personally I felt the ER6i's bass is just about right, I think it is really down to what song you listen to, as well as what volume you're listening at.
When I had a perfectly good seal, I could hear crystal-clear bass (although not strong enough for most people). Using an equalizer might help in that respect, since the ER6i's bass response is very bad at low-volume, if you crank the volume up it sounds a lot better.
You need an NUS Extra card (£10 for 12 months) - http://www.nusextra.com/discounts/amazon/