The route is a fictitious Ex LNWR line, (now a preserved line) so the stock in the background is fine. The "errors" are loco specific. You are extremely close with the number guess.is it that the two pieces of rolling stock in the background are out of region/era? The coach looks quite old (from the letters I can make out it night be London North Western Railway) and maybe the other thing (which I'm guessing is GWR with the W obscured by the funnel) is far from the GW?
If not, then an alternative guess is a non-prototypical loco number.