although your insured, the only way the police can check is by using this database. So if your not on it, the police pretty much suspect your not insured. If they want to be funny with you they could, under suspision take your car off you, and like i said, ive heard it been done.
Most major insurance companies are signed upto this.
Like i said, have a word with your insurers and ask if theres anyway you can be added.