i invented a way round that problem.
buy a 10m telescopic pole from skyblue lesuire.
buy 15m of 10mm OD hose from hydrasun.
buy a thin car wash brush from vikan or similar (wheel wash i think). the ones that will fit through the barriers.....they must have a hozelock connection on the bottom...explanation coming

use a hozelock fitting (normal ones that you can get anywhere)
put the hose up through the pole........force the hose up the hole of the hozelock fitting and then clamp onto the pole using the hozelock clamp.
fit the hozelock brush into the hozelock fitting and there you have a pole with brush dedicated for barrier/juliet windows.
remember these poles are clampless, so you will need to hold the base of the pole to keep the pole up.
sounds complicated, but its very simple.