So, yes, it's more complex. I don't think anyone would suggest parliament would just rewrite arbitrary laws on a whim, because there are complex dependencies (hello Brexit). The point is there is no legal hindrance to it, and that is almost unique (I write "almost", but I don't know of a single other country where parliament has so unfettered power - I'd love examples).
> If the time should come when our Parliament deliberately passes an Act with the intention of repudiating the [EU] Treaty or any provision in it or intentionally of acting inconsistently with it and says so in express terms then I should have thought that it would be the duty of our courts to follow the statute of our Parliament.
or see Thoburn v SCC which established that constitutional statutes (such as those establishing the primacy of EU law) are only protected from _implied_ repeal.
The reality is somewhat more complex once you consider the UK's treaty obligations, many of which are hard to reconcile with "pure" Dicean sovereignty, but it's a good starting point. As a counter example, the UK can't practically legislate in a manner that breaches the ECHR (European Convention on Human Rights - completely unrelated to the EU). Similarly, while still a member of the EU the UK, like all EU members, has to accept the primacy of EU legislation over domestic statutes in the areas in which the EU has the competence to make laws.
Studying the uneasy relationship between dicey style sovereignty and EU legislation (hello "Factortame" cases...) was a core component of a law degree in the UK for the past few decades, I assume this will change shortly given recent history!