I'd try lapping the bore, if theres any rifling left that is, then using cast boolit handloads. If not you may be able to fit a No.1 MkIII SMLE barrel to the action.
The sights would require some careful work to remove and remount on the new barrel.
PS
According to this
http://www.thefreelibrary.com/Enfiel.....-a0225252360
The Martini and the SMLE have the same shank threads and diameter.
Its mentioned that during WW2 some Martini Enfields were rebarreled with SMLE barrels.