From the dates, and the fact that you're speaking English, I'm going to assume you're British; in that case, the 'official' place to go to to see if anyone is interested would be the Imperial War Museum. I'd suggest having a look at their collections policies and what they're currently acquiring, and filling out a donation form (if you want to donate it).

If they're not interested, or you don't want to donate it to such a large institution, it might also be worth checking with any local museums - smaller institutions are often very eager to get local history like this, especially if your great-grandfather survived most of the war!