My 11 plate Fabia Monte Carlo 86 makes an odd noise when switching down to second gear, just after lifting the clutch, it's sort of like a rattling but also sounds like a loud motor burning out perhaps?

Doesn't do it in other gears so far, only time I hear it is then

Known issue: The engine has a constant knocking noise while stopped and revs are below 1000, not sure if this could contribute to the problem.

The knocking noise I under 1000 revs will be the fuel pipe on the bulk head