I think there is no doubt the most representative PSB songs are:
"West End Girls":
Number 1 in: New Zeland, Norway, Canada, UK and USA.
Best Single at The BRIT Awards
Best International Hit at the Ivor Novello Awards
Ivor Novello Award for Song of The Decade between the years 1985 and 1994
Arround 600.000 copies sold
"It's a sin":
Number 1 in: Austria, Finland, Ireland, Germany, Italy, Spain, Norway, Poland, Sweden Switzerland, UK
Arround 300.000 copies sold
So answer the poll.
By the way, the other one is not a PSB written by them (if not I had included it in the poll):
"Always on my mind":
Number 1 in: Finland, Poland, Sweden, Switzerland, Germany, Spain, UK (Number 1 in Official European Chart), Canada
According to BBC: all-time best cover version
According to Daily Telegraph: the second all-time cover version