Yes, I think I need someone like you to design a garden at my house. My home is new construction on a piece of land that had no trees or any landscaping whatsoever. So just trying to get started with it, more so this coming Spring. Right now, all I've got are a couple of Red Maple trees and one Crepe Myrtle.
Thanks to the Jet Stream, I think you guys get plenty of rain and moderate temperatures year-round in England, especially at your northern latitude (perhaps Scotland being more of the exception to those moderate temps). So, I am sure your garden thrives.
Here in the southeastern US, our summers are very hot and humid. And even though we get more rain than out west, I think our peak temperatures in summer stress a lot of plants to the max, unless they are well taken care of. I do have an old friend who has a garden that seems to thrive (a little bit like yours). But it's under a canopy of large trees - and I think that makes a big difference, especially in this climate.
This is why Crepe Myrtle trees are so popular in the southern US. They are heat tolerate down to around 0 Fahrenheit or (I think) about -17 Celsius while at the same time thriving in our long, hot summers, without the stress factors of so many other plants. But landscaping with Crepe Myrtles "only" (along with standard shrubs that many folks plant next to their home in the front of the home), could be considered boring by many who are into (or getting into) landscaping and gardening.