JDR
Nice looking carbine!  What a find and in the UK no less.  Good for you.  You've definitely come to the right Krag forum.  These guys are a tremendous wealth of knowledge and great resource.  A couple more pics will be of help.  The muzzle crown and sight area.  Closeup of the rear sight (looking for the "C").  Barrel length from the bolt face to muzzle.  You can use a cleaning rod down the barrel on a closed bolt, then mark and measure.
Vic