I wouln't rely on it mate!
When shopping for insurance before i bought the 1.2, most companys that would insure me were quoteing £3000 - £3500 but like yours, there was a company that offered it alot cheaper (just over £500 cheaper)
Obviously i was chuffed as i now had more money to put towards a car.. Bought the car, rang the insurance company, checked through the details and they quoted £600 more than what it was on the comparison site. All my details were correct ect.. basically i was f*cked
If you can do it all online then buy it now lol, your only £20 out of pocket if you dont get the car and if you do get it, you've saved yourself a fortune!