Gook UK orientated collection of Bonsai Videos from Graham Potter Potter, search for Graham Potter. I tried posting direct link to list of his videos, but it displays incorrectly. His cultural advise is for UK, and he is an excellent teacher of technique. Tends to work on larger material, but the techniques of wiring, shaping and pruning all apply to smaller trees, just need to scale down what you do.
The reason trees need to be outside day & night for as much of the year the temperatures allow is the temperature change between day and night is important for their metabolism. Trees use the sugars they produce during the day to fuel their cell growth, day and night. During the day, its warmer, and they use the sugars they produce at a high rate. At night it is cooler, and they use less sugars. A 7 to 10 C temperature change between day and night allows the tree to accumulate sugars, which can then be used for growth. If you bring your trees into a warm house at night, the tree will use up most of the sugars it produced during the day, leaving little left over for new growth.
Since it is autumn now, and your trees have not had time to acclimate fully to winter. I suggest leaving them outside, except on nights where it will drop below 0 C, or 32 F. IF you have an unheated sun porch or other area that stays frost free but cooler than the living area of the house, move them there when temps dip below freezing. This is call the "dance of the trees" when you have to keep moving them all the time. Next year, after they have been outside all summer and naturally acclimated by experiencing a lengthy autumn, you can leave them out all winter. But this year you will be stuck with having to protect them from below freezing.
Even though Loropetalum is a "hot weather loving" tree, it does need a cool dormancy to grow well in spring. The azalea likes cooler summer weather, most of the UK is perfect for them. Azalea too need a cool rest to initiate the spring flush of growth.
For 100% indoor plants, look for true tropicals. Ficus is perfect for the generally low light levels of most indoor settings. Artificial light gardens can be bright enough for sun loving tropicals if one sets them up right. Eugenia and other members of the guava family do well in bright light set ups indoors. Also Malphigia, (Acerola) does well under lights. There are many more. Explore.
