Obviously the issue you have is an age restriction but those insurers who offer day insurance will more than likely have either the age restriction or a minimum value.

Do you have a current insurer that offers you cover? Perhaps they would cover you for the day.

If not have you tried the normal insurance companies. Note though that most don't like to double up insurance companies.

Try http://www.aviva.co.uk/short-term-ca...formation.html

I can't see an exception on either age or value. They may be your solution.

HTH
Tim