with NFU and said I would use it for work purposes only and its only £200 a year
Yes do this, or insure them as a named driver on your insurance. Both of these options work out much, much cheaper (until they have an accident) than getting them their own insurance.
Until the insurance company does their homework in the event of a claim and your insurance is invalid. NFU only works for certain postcodes.
Personally I’d spend the Grand on a RTW air ticket at that age but you do what you like.