As with the previous response - I would not normally get engaged with this sort of dialogue, however seems this is a tricky one to solve.
My streaks were not as bad being the result of only a few years.
I googled and found the cillit bang solution, I could not find the exact product tried the white one, another bathroom cleaner and epic fail.
I also found a thread where someone recommended Hob Brite - so off I popped to Poundland and sourced some.
Applied with a damp cloth, left for 10 mins - cleaned off with hose and mop, major improvements a few little white marks ( probably down to my ineptitude in application )...... if I did it again I am sure it would be completely clear, but even now it is more than good enough.
So Try Hob Brite