I find that the best tool in such a situation is a piece of paper.
On it will be prionted a message indicating that in order to clean their windows, I need better access.
I wrote on one today. Not a gate issue but the side alley was totally blocked off. I haven't dumped - though they won't get a clean from me this time around. I've merely given them the opportunity to continue with the service by ensureing better access in the future. If it's the same next time, that will be the finish of that job. I'm not being unreasonable either. It would have taken ages to get through if I had tried.