On the same £65,000 gross, a worker takes home roughly 1828 zł more per year in Poland than in United Kingdom. That gap reflects the tax structure alone — before rent, healthcare, or savings behaviour come into play.
Housing is the first multiplier. Poland has moderate rent pressure, while United Kingdom has high rent pressure. That keeps Poland's nominal advantage closer to a real-world advantage.
Healthcare and pensions go in the opposite direction. Poland runs a public healthcare model — NFZ public system with growing private supplements. United Kingdom uses a universal model — NHS provides universal care funded from general taxation, with private top-ups. The country with lower take-home often shifts costs that the other country leaves to your private budget.
Net-of-everything, a relocation decision should weigh strong public welfare in Poland against strong public welfare in United Kingdom, plus differences in pension capture, social safety nets, and city-level cost of living.