Funnily enough I grew up in Eastbourne. Your best bet is to contact (and visit) the Redoubt fortress military museum on the seafront. The museum covers local military history from the napoleonic era through to modern day, so they should be able to help.
It's also a fantastic museum, and napoleonic era fortress, to visit.
https://en.wikipedia.org/wiki/Eastbourne_Redoubt
http://www.eastbournemuseums.co.uk
If you are in the area, Newhaven fort is a short drive and also well worth a visit.
http://www.newhavenfort.org.uk
Further away there's also Dover castle, including an underground hospital and the bunkers where the Dunkirk evacuation was planned and commanded.
http://www.english-heritage.org.uk/v.../things-to-do/