I have a save file with 2 Mews, one from an Australia event and the one I got in Spain. Both Mews have the same IV but different trainer name and Id.
Australia: HP 5, Atk 10, Def 1, SpC 5, Spe 12, TID 20824, OT NAL (level 100, EV trained: 383 288 270 278 292).
Spain: HP 5, Atk 10, Def 1, SpC 5, Spe 12, TID 01495, OT EUROPE (level 5, no trained: 25, 16, 15, 15, 16).
I got the one from Australia around April-May 2000 and the Spanish one in July 2000. My assumption is that every Mew from that time had the same stats, it would be much of a coincidence that the version in Australia and the version in Spain had the same. I haven't check other posts on this forum but I would bet the UK and Danish versions are the same.