I tried putting your plant through PlantNet and with a 50% confirmation rating it came up with Chinese Helwingia (Helwingia chinensis Batalin). I don't have any experience with this but this might give you a starting point to confirm id.
thanks, i believe that is what it is , a rare shrub that is epiphyllous flowering, https://www.burncoose.co.uk/site/content.cfm?ref=Helwingia - Growing Guide A curiosity of a shrub from eastern Asia from the Himalayas to Japan. It is found in forests, woods and thickets on mountain slopes and along roadsides and streambanks. The flowers are epiphyllous, growing directly from midribs on the upper surface of the leaves.
I'm far from convinced that it is Helwingia! Yours has a narrower, more lanceolate leaf with much more prominent spine-like tips to the veins, and also shows small stipules on the younger leaves, which I can't see in photos of Helwingia.
That's a better match on leaf shape, but it still lacks stipules, and has a different branching structure, with less succulent-looking shoots.
We used to grow Helwingia chinensis. Below are my pics , showing the tiny flowers growing from the midrib Not sure if your mystery plant fits.
