Hi, I'd leave the plants on the window. The photoperiod will be reduced naturally as days get shorter in the autumn. The plants will still be photosynthesising to some extend so will need light. My VFTs are growing new leaves even in winter and they're outside in a cold frame (even the Beast from the East didn't stop them).
Also, windowsills are generally the coldest part of the room (if the heating is turned off). You really need to maintain the temperature below 10 C (preferably around 2-5 C) for the plants to have proper dormancy and reasonable humidity (that shouldn't be a problem if there's no heating and the window's opened). Ventilation is also important to prevent fungus problems. All you have to do is reduce the watering, keep the plants damp but not waterlogged. As a rule, for outdoor plants dormancy should start around Halloween and last till Valentine's Day (or longer depending on weather; dormancy shorter than 3 months will not be enough). If you're hand feeding your plants, stop by the end of September.
I would also suggest you look up plants that don't need a dormancy. There are lots of CPs that can be grown indoors all year round, some may need a terrarium/artificial lights but not all. They may be more suitable for your growing conditions, unfortunately temperate plants don't do very well in flats in the long term.