looks pretty right to me on the calcs. I believe Westnet has an undrawn 90mil facility, but receivables/payables spread around $74mil (credit i.e. more payables) at 30 June 2008 so pretty much the same.
PD Ports facility may yet be refinanced before Feb 09 as well. If not I see the possibility, like you, of a small shortfall in Feb 09 until PowerCo monies received. No bank with a commercial mind would not extend for one month to ensure they receive their money.
Cheers
BBI Price at posting:
9.8¢ Sentiment: LT Buy Disclosure: Held