Can someone tell my why the government isn't just buying it back at this point?

Thames Water has previously said that customers will not be on the hook for the interest on the £3bn loan

I mean, there's no direct liability, but I'm operating on the assumption that the company's source of income is going to be its customers, and that's the only way it could repay said loan. So even if indirectly, it's gotta come from their pockets.

I guess if the government nationalizes the company, then taxpayers might wind up paying for the loan, but aside from that...outside of managing to convince unwise creditors to lend more than the company assets are worth and then having debt discharged in bankruptcy, I don't see who else would eat the cost.