Just threw this list together. Players that have previously played in the NRL that have been in the English superleague in 2007 (so still currently playing). To be honest I'm surprised there's so many.
Aaron Gorrell (Dragons)
Aaron Moule (Storm)
Adrian Morley (Roosters)
Alex Chan (Northern Eagles, Eels, Storm)
Ali Lauiti'iti (Warriors)
Ben Harris (Bulldogs)
Ben Jeffries (Dragons, Wests Tigers)
Brad Drew (Panthers, Raiders, Eels)
Brent Grose (Rabbitohs, Sharks)
Brent Webb (Warriors)
Bryan Fletcher (Roosters, Rabbitohs)
Casey McGuire (Broncos)
Chad Randall (Sea Eagles)
Chris Flannery (Roosters)
Chris Leikvoll (Steelers, Dragons)
Chris McKenna (Broncos, Crushers, Sharks)
Chris Nero (Dragons)
Clinton Toopi (Warriors)
Daniel Heckenberg (Eels, Dragons, Sea Eagles)
Danny Lima (Roosters, Raiders, Northern Eagles, Sea Eagles)
David Solomona (Roosters, Eels)
David Vaealiki (Eels)
Francis Meli (Warriors)
Glenn Morrison (Tigers, Cowboys, Eels)
Gray Viane (Wests Tigers)
Henry Fa'afili (Warriors)
Hutch Maiava (Bulldogs, Sharks)
Ian Henderson (Eels, Roosters)
Ian Sibbit (Storm)
Jamaal Lolesi (Raiders, Bulldogs, Wests Tigers)
James Evans (Raiders)
James Gannon (Tigers)
Jason Cayless (Roosters, Eels)
Jason Croker (Raiders)
Jason Hooper (Steelers, Dragons)
Jerome Guisset (Raiders)
Joe Vagana (Warriors)
John Skandalis (Magpies, Wests Tigers)
John Wilshere (Storm, Reds, Dragons)
John Wilson (Eels, Wests Tigers)
Justin Murphy (Warriors)
Karl Te Mata (Warriors)
Kevin McGuinness (Magpies, Wests Tigers, Sea Eagles)
Kylie Leuluai (Tigers, Wests Tigers, Eels, Sea Eagles, Roosters)
Lee Hopkins (Panthers, Eels)
Lesley Vainikolo (Raiders)
Luke Dorn (Northern Eagles, Sea Eagles, Roosters)
Luke Quigley (Knights)
Mark McLinden (Raiders)
Mark O'Neill (Tigers, Wests Tigers)
Mathew Head (Dragons)
Matt Gafa (Raiders)
Matt Gidley (Knights)
Matt Sing (Panthers, Roosters, Cowboys)
Michael Korkidas (Roosters)
Michael Sullivan (Northern Eagles, Sharks)
Michael Vella (Eels)
Michael Withers (Tigers)
Motu Tony (Warriors, Broncos)
Ned Catic (Panthers, Roosters)
Pat Richards (Eels, Wests Tigers)
Paul Rauhihi (Knights, Bulldogs, Cowboys)
Phil Bailey (Sea Eagles, Northern Eagles, Sharks)
Richard Swain (Mariners, Storm, Broncos)
Sam Obst (Roosters)
Scott Donald (Cowboys, Eels, Sea Eagles)
Scott Hill (Bulldogs, Mariners, Storm)
Shane Elford (Panthers, Wests Tigers)
Shane Millard (Roosters, Magpies, Rabbitohs, Dragons)
Shayne McMenemy (Magpies)
Shontayne Hape (Warriors)
Sid Domic (Broncos, Panthers)
Stacey Jones (Warriors)
Tame/Gary Tupou (Broncos)
Tevita Latu (Warriors, Sharks)
Thomas Leuluai (Warriors)
Trent Barrett (Steelers, Dragons)
Vinnie Anderson (Warriors)
Willie Manu (Wests Tigers, Rabbitohs, Dragons)
Willie Talau (Bulldogs)
Also Rod Jensen was on TV last night playing for Huddersfield in the playoffs supposedly! Although that might be one of those temporary finals stints.