If you have previously been banned or currently have lots of penalty points you can still get insurance but most likely at a higher rate.
If you've had an accident don't get any repair work done until you have cleared it with your car insurance company first. It is possible to choose a car insurance company who have agreed car repairers, to save you driving around getting quotes. They normally gaurantee their work also.
Voluntary excess is an agreement you make with the policy provider to pay a higher percentage of excess at the time of an insurance claim. This also means it would be unlikely you would make a claim for a small amount of cash and risk losing your no claims bonus.
Until your insurance company issues you with a cover note or a new policy then your car is not insured. That does not mean you need to have recieved your cover note. Many comapnies, give you instant cover, where the agreement is there imediatly.