Look in the metal detector forum......some of your questions are answered in there.
Basically if you dig something up and have no idea what it is, OR you identify it as containing explosives......WALK AWAY.
Take it from me, anything that contains explosives is dangerous. Doesn't matter if people say 'Oh yeah ! I've been emptying amatol out of shells for YEARS and I'm ok' or 'If you find one of these, you can hit it with a brick and it won't go off'...........it ain't worth the risk.
I am like John (above) and have dug France and Belgium as well as the UK. There's still plenty of stuff out there that will remove your fingers, hands, arms and torso before you can say 'bang'. Just dig slowly and identify what you've found before you take it out the ground.
And those guys having a go at you for metal detecting.....if we didn't, the history would be lost forever.