Some countries do impose a minimum period of passport validity upon visitors seeking to enter their country. The reason is usually that they require you to have a valid passport throughout your entire stay (which might, for example, be unexpectedly extended if you had to go into hospital).
However (assuming that you hold a UK passport, or one issued by any other EU nation) you're NEVER required to leave any EU member state. You could enter Germany on 25 November and stay for a decade or longer if you liked. (You simply need a valid passport to get in. When you leave is irrelevant). So it's impossible for any EU member state to impose a minimum passport validity on any EU citizen.
i.e. a UK (or any other EU) passport is ALWAYS valid for entry into ANY EU state, right up until the very last second of its nominal validity (although, if you're coming back, it's clearly a good idea to ensure that it's valid for your return journey too!)