Looks like Silene vulgaris,Bladder Campion

Poinsettias are sprayed with growth retardants to keep them small. When I first moved to FL, I worked at PanAmerian Plants (Now Ball-PanAm)and helped grow poinsettias. One year, someone mixed the growth retardant wrong and burned the whole crop. The flowers on that one look like a Christmas Rose poinsettia. I've seen them hanging over the top of an 8 foot wall in Plant City. I've never been able to get a store-bought one to survive. It's hard, because it can take them years to grow out of the growth retardant. They're hard to root. You have to "seal" the bottoms with a lighter or by touching it to a hot stovetop (covered with aluminum foil so as not to get the sap on the burner) to stop the sap from flowing out, and they need a lot of humidity. I got one to root once by making a "greenhouse" with a 1-gallon pickle jar over the pot.

a mystery to me, KK but I'd like to know. Did you receive an answer elsewhere? If not, can you say where it came from and are you agreeable to my sharing the photo ?

You're welcome. Am sorry to say, no you've used things that are good for gardens, but not succulents. Good they've got drainage holes. Sadly you've used the wrong mix & in a bad way. It's been shown that gravel on the bottom doesn't help drainage so pls, nothing special on the bottom. If you're in the UK, I think compost just means soil. In the USA compost means matured, decomposed organic materials rotted down as it were to make soil. Very different things. Vermiculite holds water, not what these plants want. They need the opposite, fast draining mix. I would redo it w/ Cactus & Succulent mix (avoiding peat if you can) & Perlite, mixed 50/50 percent. Importantly, when repotting succulents, pls. don't water them in, just bang 'em against the table if you need to settle the soil, use rocks if you need to prop the plants up, but wait 3-5 days before watering. Any searches here for suggested mixes for succulents will give you lots to read & comparable search on care will do similarly for care. It's considerably different care than that w/ which you seem familiar. Lena