It’s been a while since my politics A level, so I may get some of the terms wrong but hopefully the facts right.
As the UK doesn’t have a formal constitution, it relies on convention and that parliament is effectively all powerful (under the crown) in that if parliament (encompassing both houses in this context) votes for something it can do it. (As it represents the will of the people and has the authority of the crown (less relevant in the modern day))
Parliament can’t therefore lock a decision in such a way that a future parliament can’t change because the future parliament is still all powerful.
In practice though this isn’t entirely the case. You can make a law like you said, and while a future parliament can break it, it would (probably) look bad on them. But what does that do to stop politicians?
A further note on the previous chain - we go have two houses of parliament; the house of commons is the main one with the green benches that most will recognise. It has our elected representatives (MPs) in and (normally) where the PM is selected from.
The house of lords (red benches, appointed members for life) is generally considered the check chamber. It used to be able to block laws entirely, but I believe lost that power semi recently and it can now be overruled by the commons after 2/3 rejections.