Ann: Annual Report 2018, page-300

WPL can fund with debt it's developments so it's largely immaterial on cashflow, the reduced government take in early production may reduce debt needed to fund Browse, however the announced likely reduction in equity from Scarborough should more than compensate. And WPLs cost of (new) debt is around 2-3%
SNE is largely immaterial to being able to fund WPL growth especially at low oil price scenarios where cashflow is needed. LNG projects generate cash / cover base buisness overheads from about $9/boe, while, while downside protection in long term contracts mean even at $10/bbl Brent WPL would receive $25-40/boe (in other words WPL can under any oil price fund its base buisness + some growth). High oil prices where SNE can generate reasonable cash, WPL won't need that cashflow to fund developments.

I have no idea what you mean with spot purchases...