IDK about simplyinfinity, but here in NZ, the last mile of internet infrastructure (the fibre from homes to the exchange) is owned by regulated companies which must lease access to them at set rates or lower, and mustn't act as ISPs.

As such, we have dozens of ISPs with their own backend infrastructure, all sharing the same last-mile, and most available nation-wide.

That said, they're all going to be buying transit from a big backbone ISP to get overseas connectivity.