On 28 Feb, 16:05, me here wrote:
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?

I find Cillit Bang works well on that sort of stuff. However, don't
pay whatever outrageous price they charge for the real stuff. Your
local pound shop will have "Sonic Boom" which as far as I can tell is
exactly the same stuff for £1.