Have a search online for prices and then go along to your nearest dealer and see what they have on their stocklist and what deals they can do.
I started looking for a 6 month SE-NAV and managed to pick up a brand new one for around £500 more. If looking at new go to Vauxhall website and you maybe lucky to get a voucher if taking a test drive - think I got £350 and then partners discounts.
Good luck and happy hunting.