Apologies are a way to acknowledge that mistakes were made in the past as well as that there's an intention not to make them again. As such they help us prevent future mistakes.
As such I don't see how this apology will make one jot of difference to the UK governments future actions (it already has openly gay MPs, I can't see them backing legislation that criminalizes their sexual preference).
So the United Kingdom (represented by its Home Office and judiciary in the 1950s), as a thing with a corporate identity, did wrong to Alan Turing, and it is appropriate for the United Kingom (represented by its Prime Minister) to apologize for its misdeeds.