I have just sold a not in the wrap No4 Mk2 that had been cleaned but not used to a service rifle shooter.
You can buy no drill and tap mounts for these rifles. The steel one is the best only down side it may only be 1" tube diameter.
They are not made anymore, they are already old, they are still new so the value will only go up.
Clean and shoot one, keep the other two as an investment. The shooter will still increase in value as long as it is left unmodified. You will have the best of both worlds.
I had two Mk2s with the idea of shooting one and keeping the other as new but a mate offered me enough to prize the one i was going to shoot away from me at a weak moment.