Hi to update on this, Neff sent an engineer.
He said straight away it shouldn't do that and thought it was the fan blade catching. They ordered a fan and came back after 2 weeks to fit it.
It then did it again! After further checking he discovered it was the piece of metal on the bottom of the heating element.
The catalytic cover on the back fits over the fan and element but the element bracket was just catching on the bottom and making a clicky/twangy metal on metal sound.
Abit of twisting and adjustment and it stopped. Used the oven and no noise now at all.
I found him very helpful and a nice guy, infact he only lives just down the road!!
Maudlinmanda - When you first contact Neff they'll say it's expansion and disregard it. Then with persistance they ask for a video.
If you have any issues refer to my case and the info above. Yes, it was expansion but it wasn't a normal noise and should be put right.
Nothing really wrong with the oven, just a slight incorrect positioning of the element bracket. The engineer had never experienced this before so it's worth pointing this out if the noise persists.
Roselily, I think Bosch and Neff and pretty much the same oven but look different. Depending on the model there are slight variances such as full catalytic or just back and top etc.
If you ever need an engineer (hope not) then it's the same company for Bosch, Siemens and Neff.
The engineer told me alot of cheaper brand ovens now are all made in Turkey with different fronts and brands and mass produced.
Bosch/Neff are well built. I'm sure you've made a great decision.
I find ours cooks really well, even and heats up quickly and is now quiet too! I'm sure your Bosch will be the same :-)