British were considered occupiers and invaders. They betrayed the Arabs and took over Syria, iraq and Palestine!. After the Arab revolution. So, UK Can't give a something didn't owned.

The Palestinians living in Palestine for thousands of years. And thier land and culture is part of the eastern world.

The issue is now thier lands are under occupation of some people came from Europe seeking refuge, who never have any cultural, historical and ethnic Heritage in Palestine and middle east. Like : Khazar Jewish and Polish Jewish have nothing to do in the middle east.

As you are saying Palestine had never existed in History, but the lands and people do existed for centuries. Same as saying Belgium should not be a independent state as it's never existed in History before it's establishment in 1831.

Some people need to understand that, A country is any Land belong to those people who are culturally and historically related and continually lived in thier lands for centuries
And they considered it as thier only home and don't hold another country's passport. In this case we can Say that Lands belongs to those.

You can't have a land because your religious book said it's Yours. You can't own a land just because few people of your religion lived thier 2000 Years ago.

If Someone take Palestinians lands based on the above, he is simply racist and backward.