Chris did you notice if it was already off its grippers where it shrunk? This would normally be across door bars or if they have pulled it up to put their speaker wires underneath.
I've never experienced shrinkage from an Axminster unless it was already flapping about at the edge.
Obviously nothing you can do about it now but for the future always go round on hands and knees and test the fitting, it really is worth it.
p.s. the width is probably more likely to come untucked from the grippers: Axminster isn't flexible width-ways, making it more difficult to tuck in behind the gripper so it will come out easier.
pps. I can't remember the theory exactly but I thought it mostly shrinks in the length because the jute wefts expand making the cotton warps have to travel further round them, hence the top and bottom ends getting closer together. Could be wrong though, I will stand corrected