I don't know if my door is B1420, but it must be similar. I bought a pair of 10mm diameter superstrong magnets from Maplin at about £9, and stuck them on each end of the top of the oven facing the door. Works wonderfully!
Previous attempts with slipping washers under the spring bracket, or straightening the bracket, had helped, but the magnet thing is great.
I have heard you can get free magnets from a helpful computer fixer who disposes of dead hard drives, which are apparently fitted with similar megamagnet stuff.
lionel, May 2010