Beetles/Weevils eating leaves

Well actually my mother's leaves...

Need help identifying and eradicating a pest in my parents' garden. It's attacking a rhodedendron-like plant.

Deep green, flat, beetle-like creature. Hard to spot as it's the same colour as the leaves. About 6 legs (maybe 8). It has a light brown half-diamond-shaped section at its tail end (again, looks like a dead part of a leaf).

It's not a root weevil, I've seen pictures of those.

These things are eating her plants alive. They're also mating like crazy at the moment (at least that's what it looks like they're doing).

Hi Extopia
Sounds like a cockchafer. If you can catch one a bring is to the garden centre they will identify it for you. Any contact insecticide should kill it. Good luck.
HP

A pesticide is not necessary.Shake the bush so they fall down.These beasts play dead man as soon as they are disturbed and they are very slow to get back to the bush,it takes them ages.If you don't have the time to shake the plant once or twice a day there are also strips of glue/sticky tape available from the better garden centers to be fixed around the stem.
Hanging up a few nesting boxes for the titmarches would also solve the problem.