Bliss,
Why couldn't he sign your licence?
As a JAA TRE he should have been able to handle all the paperwork on the day........ All you should need is his signature with his JAA TRE and sim number entered on the correct, completed form (CAA 1158 I think).
I'm a TRE and have so far not found any problems with doing checks for other JAA pilots.
As DFC says though other states may need extra details.............
Edited for spelling !!!!!!!!!!!!!!