[Oliver_W]

There is a precedent for a Monarch dismissing a Prime Minister - William IV kicked Lord Melbourne out as PM, and appointed a minority government.

The new government quickly fell apart, and Melbourne was reinstated and was PM for a further 6 years.

As a result, the Monarch (technically) lost the ability to choose members of their Cabinet - or rather, they'd "choose" them upon the "advice" of the leader of the largest party in the Commons, who would be the now-implicit "choice" for PM.

My point is, Charles technically can dismiss the current Parliament, but unless there's a literal bulging majority in his side, both in Government and the wider population, it could cause further changes.