Hi, i just had a little accident with my honda fit 2012 and my front left quarter window has broken. I have found one from an earlier model (2008)

Can anyone please tell me if it fits or not?

I am aware that the bumpers, bonnet, mudguards and mirrors are different but also know that the doors are same.

 

You can't say this too often about the FIT, but in your case it won't fit.
2007-2008 front quarter window is considerably smaller than the 2009-2013 ones.

The doors are NOT the same.
I don't know if they will fit in between different generations, but they are definitely not the same and it will look out of place. The GE (2012) door has 2 profile lines that are not found in the GD (2008). Just take a look at photos of the 2 generations and you'll see.