I have a build-up of soap scum / lime scale on the shower screen.
previously this has been dealt with by steam cleaning once it got too
much for proprietary shower sprays to deal with. Then a combination
of meths and/or lime-scale remover followed by steam cleaning seemed
to be necessary. Now I cannot remove the damn stuff at all.

Done vinegar too, btw. We spray after each shower with whatever that
shower-spray stuff is, which does prevent it getting worse; but
there's still this residual blemish that nothing seems to shift.

Any suggestions?