These £15 JVC plugs (http://www.currys.co.uk/martprd/store/cur_page.jsp?BV_SessionID=@@@@1280499264.1185129739@@@@&BV_EngineID=ccgeaddlhlmjlffcflgceggdhhmdgmi.0&page=Product&sku=234228&fm=0&sm=7&tm=undefined) are pretty good for the money, they come with two sets of marshmellows.
Theyre pretty good at killing outside noise and likewise if you sat on a quiet train with these on you wont get dirty looks. Very bassy, but if you push em too loud on a decent hi-fi they distort easily. Theyre pretty flat mid to high but nothing a bit of eq cant sort.
shure headsets < cheap options.