Welcome Richard. Is yours the facelift version or the original one. Rattle from instrument cluster is not something I've seen mentioned on here, I wonder if there is a loose screw or clip behind?
Anyway, something your dealer should sort out for you.
My GLA rattled like an old banger from day 1 especially over coarse road surfaces. It went back to Mercedes at least 5 times including for several days at a time - probably 10 days in total. The air vents have all been replaced, the seat belt mechanisms and in the door panels. It is now much better but still get some rattles but it is just too much effort to keep chasing MB. It has also had problems with the drive shafts (now replaced), tailgate opening by itself, complete failure of intelligent light system (headlamps filled with water and corroded electronics), 5 days to get a new run flat tyre after a puncture - it was probably off the road for 25+ days in the first year.
As someone who has driven E320's for many years, I have to say the GLA I have is not built to anything like the same quality as the E320's, a fact confirmed by the local MB Service Manager.
It will be a very interesting choice when it comes to be replaced but I think it will be unlikely to be another Mercedes after 35 years of continuous Mercedes ownership