Any question answered...

HG window cleaner concentrate

Meths.

You are using white vinegar /non brewed condiment.

Have been using citric acid/lemon salt to clean the shower/bath and it is great removing limescale marks.

Non- wanky/natural glass cleaner, I’m afraid. The stuff full of chemicals works best!

As said, plain old supermarket spray window cleaner works best. It has a little bit of vinegar in it, but only to acidify the cleaner I think. This whole fad of cleaning everything with white vinegar does little other than make the house stink of fish and chips.

Don't use too much, like one spray per window. Wipe the window down until it's dry, turn the cloth over and use the dry side to wipe the smears off. If the windows are really dirty or greasy (e.g. kitchen) it'll take a couple of goes before they'll just wipe clean and smear-free.

Get some of this
https://www.amazon.co.uk/PROFESSIONAL-WINDOW-CLEANERS-SCRIM-EXTRA/dp/B004ZVBIOC/ref=mp_s_a_1_3
Other shops are available.

Crumpled newspaper dipped in water, give it a go!