Hi & welcome! I don't think these plants go downhill, unless nothing but looking at them is done. Individual trunks don't last more than a few years, but a periodic re-do will ensure that you have your plants indefinitely.
It's so similar to the behavior of so many other succulents that get "too tall" and develop little trunks. It's the same thing you're always showing with your rosettes, Baja. I'm surprised you don't see a similarity. If left to its own devices for more than a year or two, they develop the trunk look and it's almost always advised to chop & lower them.
Leggy means excessive distance between nodes, which I don't see on the pictured plants. In deep shade the leaves can reach much larger sizes, so I don't see evidence that the light has been too low for normal temperate growth. Temperate growth being the seasonal swings that plants have when they have to come inside, at least for part of the year, and the consistent lower light for plants that never go outside at all.
The growth of temperate plants is different than that of plants that are able to stay outside in the sun all year, but it's enough for pretty soft, green leaves and annual blooms.
The blooms are why I have hundreds of these in the house for winter. I started with 1 funeral plant about 10 yrs ago, and by buying 1 each of a couple of others with different color blooms and now there are hundreds of them. The roots are hardy here, so it makes increasing the numbers very easy. In the fall, I gather all stems that are making bud and bring them in to enjoy the blooms, which usually get ruined by frost if left outside even though the plants grow like crazy between the frosts.
It's not possible to avoid eventual leaning, that's the nature of so many plants, to lean over and take root wherever it touches the ground.
It may be too late in the year to bother now, but you can put your plant(s) outside for summer when night temps are reliably above frost. Start gradually with small amounts of time at dusk or dawn to get them used to it so there is not sunburn. Then add a 30 mins or so, every week or two, until the exposure is at desired level. But don't worry about sunburn if it happens, new foliage will replace the old very quickly.
To rejuvenate, cut the tips with about 2-4" of stem attached, then stick them in the soil, like arranging flowers. Leafless lengths of soft green stem will also take root and grow. To use those, I bury 2 nodes and leave 1 or 2 nodes exposed above soil.
I realize there is a lot more sun in AL than UK, but during the winter months, at least it comes through windows better, at a sideways angle. That's great because that is when it is needed to form buds. I start seeing buds around November 1, and about 6 weeks later, blooms start to open. Some of them can last a very long time, some of my plants are still blooming. I think you would need to take them outside for summer to get that longevity but you should get some blooms on plants that look like yours do in your pics.
For winter, close proximity to an E/S/W window great. Right by an east window for winter:
In a lot less sun, the leaves are so big:
There are tons of additional pics of this plant in the plant database on this site:
Florist Kalanchoe (Kalanchoe blossfeldiana)
And many cultivars with double-petal blooms and unusual leaves:
https://garden.org/plants/sear...
If you like 1 Kal, you might like others. A discussion about any kind of Kals:
The thread "Kalanchoe chat and photos" in
Cactus and Succulents forum
