May sound cruel. but as a last resort, an invisible fence. dogs get really smar after awhile and can tell a difference between a real "dog" collar that zaps and a dummy one. My former father-in-law had one installed in his front yard.

I don't like the idea but if you can't plant anything taller than 35cm you may not have much of an option. hmm maybe a minature rose. Should keep the dogs away from the fence thus keeping them from jumping over.