Correct me if I'm wrong, but I believe red poppies grew in abundance in the fields of flanders soon after WW1 ended. Something to do with the severe disturbance of the soil and whatnot. Poppies were the first plants to recolonise the area around the trenches. I think that's why poppies are used to remember the dead.
That's it
I thought the Labour party wears some sort of red flower as well?
They do, it's a Red Rose. They used to have the Red Flag, however they ditched it in the early 1980's due to it's links to communism, although back in the 79-83 period the Red Flag was probably more appropriate!