Sugi Cryptomeria japonica. Often, though incorrectly, called Japanese "cedar" (it isn't a cedar Cedrus), due to a mistranslation of the Japanese name スギ.
"Sugi" in Japanese. I think there are nearly 20 "Cedars" in vernacular (American?) English that are not from the genus Cedrus. It's often confusing for non-native speakers : estern white cedar, eastern red cedar, yellow cedar, etc. And yes, there are many cultivars. "Bandai sugi" is a dwarf form often used by bonsai enthusiasts. A bit like Sequoiadendron giganteum, it's not easy to keep healthy as a potted tree here. The leaves are turning brown in winter but it's not deciduous. Some cultivars keep their green colour all through the seasons.
I measured the tree at 10ft and it is growing quite aggressively into a mature plum tree. I'm thinking I should probably transplant to a location where it can go vertical?
Plum does not have a particularly attractive structure, maybe just remove that and leave the conifer where it is.
