There are two separate divergences from here, which is why I thought this was an interesting question.
The first is getting rid of the marriage of Victoria and Albert. Albert was a smart man, something of a liberal, and Victoria was really in love with him. Change any of these with a different consort, and you get a very different Victorian era, and one possibility is the end of the British monarchy. You change things just by not having Victoria spend the 1860s in morning. George being effectively blind will have an effect and does not get butterflied. And of course all the successors change, there is no Edward VII or the Windsor monarchs.
The second is the effect of Hanover when the personal union with the British crown is maintained, and the possibilities include Britain getting dragged into the Seven Weeks War to Hanover not being absorbed into Prussia or into Germany. This butterflies into World War 2. And a Prussian dominated second reich sort of requires the Prussian annexation of Hanover, to augment its population and create a contiguous block of territory. Remember they annexed Hanover during the French Revolutionary wars, during a period where Prussia was sort of aligned with France.