Just as an update, they may make a nuisance of them selves, but Magpies are certainly good parents. They have even been taking on the local cats if any have gotten near their young. One cat has actualy been physicaly attacked by the parent magpies when it wouldnt get the message. The cat now has a serious complex about magpies (and the birds know it - they were seen taunting/teasing it only last night.
I do though feel sorry for the other birds though, they get absolutely no peace from the magpies. i have regularly seen recently one of the magpies even harrasing the poor old pigeons, who wer only minding their own business and doing no harm. The local blackbirds seem to have been driven off (or killed), as i havent seen or heard one for ages
SIGH!