No, I do not think it is a larch, which has gray bark with slightly different structure and the vertical cut should show a yellow pale colour with rings typical for conifer.
For the latter reason I will also rule out thuja and Juniperus, which are better matches for the bark colour.
Buddlejas grown in UK are shrubs not taller than 5m with multiple thin stems. Definitly not that genus.
Oak has a deeper bark structure with a greyish colour, and feels heavy/solid. You would have noticed that.
The bark of Populus/poplar comes close, but not the vertical cut.
Finally, I find that Robinia pseudoacacia (black locust) and crack willow matches bark and the vertical cut.
Larch
Oak