I think the main win is flexibility, you don't need as much infrastructure at your "spaceport". The payload is small so the fuel savings from launching closer to the equator would be minimal, especially for higher inclination orbits. Plus it's an easy political win to do the launches locally (the UK's plan calls for spaceport in Scotland, England, and Wales. I suppose that's their equivalent of NASA projects being built in all 50 states to spread the pork around). Plus doing launches in overseas colonies/possessions can be politically fraught. It occasionally has been an issue in France