My gut says frankenwatch on this one. To me, the dial is suspect. The case reference is legitimate, but ties in with a non-chronometer cal. 354 movement.
That being said, it was non uncommon at that time for Omega to use chronometer rated movements is some Seamaster references as an upgrade. See Ref. 2577 Seamasters. I don’t know if this was done for the Ref. 14925.
In any case, even if all original, it is not worth the £2,000 being asked by the seller.
gatorcpa