If the original medals are no longer available for official issue, you may wish to consider 'copy' medals. These are extremely accurate die-struck copies of the originals, and some dealers such as Worcestershire Medal Services are able to impress the correct naming onto the medals in the original style. These medals have the word 'copy' in relief on the reverse of each medal. Never, under any circumstances, consider having an original medal erased and renamed. My Grandfather's medals have been stolen.
Most police forces hold regular 'identity parades' of stolen goods.
Secondly, try placing the details on something like Medal Tracker, which can be accessed through MedalNet . However, if he was a commissioned officer, just his name appears on the medals. If he had a fairly common name, tracing an officer may be difficult, although officers' records from the Great War are fairly complete, and there are always the 'Army Lists' to refer to. In the case of an enlisted man, the number is his service number, which can range from number '1' to a six-digit number. During the Great War, each regiment or corps had it's own numbering system, so the same number could be shared by several different men.