I think the key point for those of you without an E.U. passport is that the Schengen system is not designed to accomodate your needs as a traveller across the E.U. this has a massive impact because we are all used to just jumping in the van and going, with no restrictions etc, people who have propertys in Spain as an example cannot get a Schengen visa, they need to get a Spanish visa, but if they drive down to Spain and drive back and the whole trip is over 90 days technically the French authorities could take the view that they have still been in the Schengen zone for in excess of the time limit, obviously common sense would be for the French to discount the days spent in Spain, but the French could easily claim that they could have moved around the E.U. and there have been cases where this has happened, those of you with a Spanish visa etc, would be well advised to keep receipts for spending (ideally a receipt each day) and if you do pop into France don't keep such and leave the phone / camera off.
In June a British truck driver returning from a trip to Turkey was checked by Dutch Police and arrested for exceeding the 90 day limit, he had calculated excluding the days in Turkey, but the Dutch police didn't agree, he paid the fine simply to get on with his trip, the RHA also has reports of similar checks within the Netherlands
here
Your UK passport effectively acts as a short term Schengen visa right now, but soon ETIAS will be required and the E.U's intention is anyone over staying will have thier ETIAS cancelled and therefore you will have to re-apply but your be re-applying with a criminal record and therefore may not get another one.