Isn't a memorial more a spiritual thing anyway, rather than something located purely for (and don't take this the wrong way) convenience and erm, dry feet?
London would attract more people, but its connection isn't as great as the Fens of Cambs or lincs, where like it or not, thats where these boys went to work, and where many of their families still live.
PS: What job do you want?!
(This is all very Famous Five isn't it..?!)