I'll bet that the CRE already exists in your saved game. Might also need to clear your BG2 cache directory.
You're right 'cause I tried it with the full filename and no joy. I think Kismet also warned me that I must not have entered the "Area" where the creature exists. Anyhow - I'll clear the cache. If that doesn't work, the fact that DLCTEP is picking it up properly means I must have coded the .tp2 correctly and I'll probably see it on my next pass on debugging when I start a new game.
Thanks all.
Note: Just tried it after clearing the cache. Doesn't work and I don't have a save game before I entered Trademeet. Kismet then is right -- can't do re-assignment after you enter the area.
Further Note: Started a new game since I have a portrait modification done in Chapter 1 - coding works so Kismet is definitely right - can't do reassignment via the .tp2 after you've entered a particular area even if you flush the cache.