My Paternal Grandfather joined up during the middle of the war (too young at the start) as a wireless operator for the RAF where he served in West Africa (Nigeria I think) and later in Holland once it had been liberated.

My Maternal Grandfather was a research scientist and consequently not allowed to fight (he worked on technology to do with telecommunications I believe). He lived in London, so enlisted as an air-raid warden instead of fighting.

One of my great uncles (I don't know anything about the others) fought in the Royal Navy as well, but I don't know very much about that.