I have bought 7 holly bushes that I want to train against a wall,
below a window, but with the plants at the end being trained up the
wall alongside the window - and with time, try to get them to then
grow along the top of the window. So the end result will be a window
in the middle of a holly bush. I have seen this at a house near me -
but have no idea how they achieved this. How do I get started?

Regards,

Ian