Book about a boy who moves to Europe, climbs a wall with one of his friends (who turns out to be a troll), and finds dragon eggs

Might this be Pillage (2008) by Obert Skye?

According to this synopsis from Goodreads, the main character, Beck, is sent to live with his uncle in a remote manor house:

Upon his mother's death, fifteen-year-old Beck Phillips is sent to live with an eccentric uncle he had never met in a remote manor house, where he learns that his family suffers from a curse that allows him to make plants grow on command and dragon eggs hatch.

This exerpt from a review at From The Bookshelf of T.B. mentions that Beck finds the dragon eggs when he climbs over a wall in the back garden of the manor:

It turns out that Beck’s suspicions are true, something strange is going on. He finds out what when he finally climbs over an abandoned conservatory wall, in the back garden of the manor. He uses his newfound talent, of instantly growing plants, to climb over the solid and very tall wall! What he finds inside is amazing! Dragons! Well, not quite. He does find dragon eggs though, and mistakenly hatches them.

And according to this Amazon customer review, a character named Milo:

reveals he's some sort of troll/magician thing