Using Squirrel for Derby on Windows

[John English]

I know this is a Squirrel question rather than a Derby one, but still: 
I've installed Squirrel on Windows 10, and the batch file to start it 
adds a load of jar files to the TMP_CP environment variable. This fails 
after the first few with "Command line too long" errors.

Has anyone got this working for Windows, and if so, how?
TIA,
--
John English