I feel for you, I would say please don’t be bulldozed, please think of yourselves going forwards.
Your neighbours aren't actually appreciating or respecting you for what you have already done to help them previously.
They now have the mindset of an “expectation”
I think it is important that you maintain your boundaries - so that they don’t feel they can “push” you with their expectations.
As others have said, it could involve a skip on your land, and contractors don’t always treat property with respect.
I think I’m a helpful person, like you, but there has to be boundaries in place - to protect yourself going forwards.
I would be asking my friends to come round at random times, quite frequently, with their vehicles, even leaving them overnight on occasion - just to preserve my position.
(In fact I am having to take the same subtle approach with 4 neighbours who are “assuming” that I am not using my own garden space, so I am currently having to encourage visitors who want to come and “chat” in my garden...just to discreetly maintain my own space)