That it is, an ARN 150. I can’t upload the full photo now, will try to do so later, but your floor.If not a 156, could it be a Class 150? Either way it's a certain Arriva operator.
That’s it, over to youClass 700?

No...but it's modern...Is it a 68?
Exactly! Class 800. Here's the full image, which I took at GWR's Old Oak Common Depot Open Day last year. Your floorThat must be an Hitachi Class 8xx unit?

That's a hard one. Class 150?