About shoulder height.
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Looks more like a Salix to me, perhaps Salix eleagnos, but I don't know the Hebe. Looks to have broader leaves from a Google search.
hanging down and the leaf scars on the trunk suggest that Hebe is correct.
... are the tetrastichous foliage, and the pale rings on the bark.
I keyed it out as Veronica barkeri in Stace, but there's no guarantee that a cultivated plant is covered by Stace. I was half expecting it to be Veronica salicifolia or one of its hybrids, but fide Stace that has petiolate leaves, and I think the photograph shows sessile leaves.
Lat/Lng: 51.1, -2.8
OS grid ref: ST440337