NHS post-operative care after a hip or knee replacement is generally competent and follows the guideline. What it is not is long. You get a defined block, and then it ends — frequently at the point where you are walking safely and independently, which is the threshold for discharge, but some distance short of where you want to be.
Walking safely is not the same as climbing stairs confidently, driving comfortably, kneeling, returning to work that involves being on your feet, or getting back to golf, bowls or the garden. The gap between "discharged" and "back to normal" is where private rehabilitation earns its place.
That is the honest positioning: not a replacement for your surgical team or the NHS pathway, but the part that continues after they have signed you off.