Answered my own question :-)
Enrolled offline licenses and the licensing client configuration file (DSLicSrv.txt) are located in:
On Windows XP:
License Client Configuration (*)
C:\Documents and Settings\All Users\Application
Data\DassaultSystemes\Licenses
On Windows Vista, Windows 7 and...
Tough one to describe but I will do my best to be clear;
Using Windows 7 x64, with CATIA V5R21SP02 I was able to check out a concurrent offline license. I can see it listed under the Nodelock Key Management (LUM) V5R21 tool, with a blue circle icon next to it.
When I go to try and start CATIA...