Well I have gained a few inches.
Same points measure 61cm.
Dealer was convinced it was ok, no faults showing on the diagnostic machine!
I insisted they take it in for a closer look, which reluctantly they did in the end.
They come back to inform, the front spring was broken. (obviously wouldn't show up on the diagnostic would it, so it appears they are only prepared to be guided by their machines)
Spring replaced under warranty, and you can clearly see the difference from the photo.