Trouble is - over here "foreign" celebs historically don't do well - Martina was first out (due to a bizarre bit of judging when the judges chose to send her home when she was bottom 2 when Rav Wilding was a lot worse than her...), and Michelle Williams was the least known member of Destiny's Child - the one everybody forgets when trying to remember the girls' names so probably didn't have a huge fanbase. Michelle probably only got as far as she did because of Brendan's popularity....
Holly and Jason last year live and work over here now, and are both well known from their Neighbours days so already had fanbases, but unless they are with a popular pro, (i know that didn't apply to Martina H) or really well known here, they don't stand much chance.. The most popular foreigner in recent times was probably Vanilla Ice doing DOI last year
Foreigners tend to do better on DWTS - Jane Seymour did well for an older lady and
Mel B and Katherine Jenkins were runners up