Totally, in the end it boils down to that. England holds cultural heritage treasures that were undoubtedly stolen/robbed and they have no intention of giving those back either.

An example is this Portugese book collection: https://www.sulinformacao.pt/en/2013/12/associacao-«faro-1540»-quer-que-inglaterra-devolva-colecao-de-livros-roubada-em-1596/