You need to weigh up the pros and cons - how much would your insurance be without any NCB, then 1 yr, 2 yrs etc. to see would it be with your while paying back yr insurance company.
What kind of accident did you have? Some insurance companies would be willing to protect your NCB if there was no injury claim for instance - you'd still have loading on your policy but, it would only be there for 12 months and then everything would be back to normal. Ask yr insurance company if they'd be willing to do this for you - worst they can say is no.
5yrs NCB is 60% of the premium - for example original premium €1000 less 60% = €400 would be yr policy price.