Fartleck training between lamp posts. Run from post 1 to 2, sprint from 2 to 3, run from 3 to 4, sprint from 4 to 5 and so on.
Its also advisable to practice quick turns whilst running - just run up and down between two lamp posts or similar. Its not just the run than ends up being the killer, the turns take it out of you too.
Further to that, apparently the bleep test isnt a pass fail on time - its all about effort (according to the AIB DVD) if you dig in and get red faced and nearly throw up at the end you'll be OK - if you wimp out and can still walk and breath afterwards you haven't tried hard enough !
Good luck