Have you spoken to Adrian Flux,,, discount available if you are a member on here.
Mine is due in a month and last year it was around 450 but I am 37 and have a clean license. Oh and my neighbours are Fergie and Roy the Keane.
Anyhow, tips from the short spell I spent working for Norwich Union are:-
add girlfriends, or parents if old and have clean licence's
don't just say 12000 miles a year if you do a lot less as this really brings it down.
Cat 1 alarms,,,,
Excess as mentioned by Mike.
Remove the courtesey car option as you lose it anyway if you specify your own garage rather than use their aithorised repairers.
Believe me in the case of Norwich union YOU WANT to specify your own repairers.
Hope this helps
Dave