Charlotte had Whiggish sympathies, which was especially evident in 1814 when the Prince Regent tried to arrange her marriage to the Prince of Orange, which wholly failed owing to her own opposition to the match, which garnered her a lot of sympathy within Parliament. If she survives past 1817, Leopold and Charlotte's home would certainly be a popular place for the liberal opposition. Catholic Emancipation would still pass in 1829, and once George IV is dead we might see the Reform Act happen a bit earlier. Charlotte would probably probably reign in a very hands off manner. We don't know much about her personally, but I doubt she'd rock the boat the way her father did. At most, we might see her make a free selection for Prime Minister much like William IV did for the last time in the 1830s; but much like Victoria's reign, Charlotte's will continue to advance the Constitutional Monarchy. She was definitely a liberal though, and well beloved by the public.
We'll assume minimal butterflies and if Victoria is born as OTL, she'll be a minor British princess. She could marry her cousin, George V (the son of the Duke of Cumberland), or maybe a son of the Duke of Cambridge. She could make a foreign match too, but given she'd merely be a niece of Charlotte's, I'd say it's likely she probably marries one of her English cousins and is domiciled in Britain. Victoria in this scenario would probably be relatively unimportant. The OTL William IV would succeed George IV as King of Hannover--assuming minimal butterflies, he'd be succeeded by the Duke of Cumberland when he dies without heirs. It'd be interesting if William IV had a surviving son in this scenario, as along with Charlottean/Carolean* (is that what would replace Victorian in this TL?) Britain we could also have a liberal Hannover. William IV gave them a constitution IIRC, which Cumberland surpressed. Either way, I think it's likely that Victoria would end up Queen of Hannover (married to William IV's alt-son or the OTL George V), or the Duchess of Cambridge.
Her survival probably wouldn't impact foreign affairs too much; the Belgians are still going to have grievances so will probably will revolt. Leopold was not the first choice to be king: the Belgian Congress originally chose the Duke of Nemours, the son of Louis-Philippe, but he was vetoed as Britain feared French annexation of Belgium. Britain will probably still be wary over French influence over Belgium, so we'd probably see a minor German prince take the Belgian throne, much like what happened in Greece. There were plenty of other Saxe-Coburg-Gothas that could take Leopold's place.
