Phone one place for a quote, phone another, tell them your last quote was for half of what it was actually for.
A lot of places will tell you to jog on but you might get lucky.
Take commuting (and maybe passengers) off your policy if possible. Commuting doesn't always seem to make a big difference but it did for me last year.
What @M_A_X says about third party might help but I've been finding TPO and TPFT quotes can actually be higher than fully comp.