you might consider an ib/ay routing that i found the other day which prices out fairly reasonably and gets you up to 2 segments on each carrier. it requires a sat. stay.......first, use ba for lhr/bcn/lhr (around $250), then:

sat: bcn/zrh on ib, zrh/hel on ay
lv 4:10p ar 5:50p lv 7:25p ar 11:15p

sun: hel/zrh on ay, zrh/bcn on ib
lv 8:25a ar 10:20a lv 12:30p ar 2:10p

on a 10 day advance purchase ib/ay prices out at around $430 u.s.......all in you get 2 segments on 3 oneworld airlines for around $680 us...