[urlhttp://www.engagesl.com/play_offs.php[/url

So,If we get beat Friday we will be at home in Week 2 playing winners of Wakey v Cats but lose our home advantage should we win and progress into week 3

Yep, you got it spot on there

If we lost on Friday, we would play the lowest ranked side that won the Wigan/Cas, Wakefield/Catalans games, so that would be the winner of the Wigan/Cas game unless Catalans beat Wakefield, in which case we would play Catalans.

So as clear as mud then