where can I find out details of LM2500 gas turbine alternators and
supporting auxiliary systems

hi, Neilbritten,

Perhaps a better way to frame your question would have been "details
of LM2500 gas turbine". An alternator is a separate equipment
altogether for generating electricity by coupling to any rotating
machine. By refering to the auxiliary systems you probably ,mean the
auxiliaries of the gas turbine.

Following address gives details of GE make LM 2500 gas turbine.
www.fas.org/man/dod-101/sys/ship/eng/lm2500.htm 
And  www.gepower.com/prod_serv/ products/aero_turbines/en/lm2500.htm 
gives details of auxiliary systems used.

Search stategy on Google:

"gas turbines"

search within results with "LM 2500"

A host of information awaits you.

Regards