Sinh,
We have several Veterans on the site, a couple of whom have posted extensively on their experiences. You should be able to get more than enough for an essay out of either thread.
Try here:
Sword Beach to Bremen., A Veterans tale. Sapper
and here also:
Lancaster Bomber 514 Squadron
As for your request of "proof of military service" this is frankly unreasonable. No one should be required to produce personal documentation for you when they are doing you a favour.
Especially a WWII veteran.
Oh, and welcome to the forums,
