Welcome, and good question. In England you likely have a good cultural understanding of the range of size possibilities of Boxwood, which is a similar plant to many of the Ilex crenata. The largest similar plant we encountered, is a 100 yr old (est.) boxwood, perhaps 18' tall, discovered in a neglected garden in eastern PA, which we layered in tree form (few branches, visible trunk). Most often the garden use for younger plants of this dense growing type is in a form called tamamono, or a half domed solid. So if you have the patience and perspective to think multi-generationally, it is possible to do as you ask. Most prefer to encounter some of the garden form in a human scale within their lifetimes. Purely a choice.