They want $700m enterprise valuation (I think).
The key is that they want a full sell down. Doing an IPO with a full sell down is difficult. Hence why the IPO might flop and Sky could have the opportunity.
A $700m valuation is pricey given that Sky is valued at $260m
The valuation of Vocus isn't an issue, it's the ratio between the two that's important. A new entity needs to be formed, with Sky and Vocus getting new shares. It's just how you slice up the pie.