Just get an MOt, write to the VW Museum to obtain an age certificate, which will serve to authenticate the year of your car with its chassis number.
When you send your V55 form to register your car, include the MOT, a certificate of insurance, the £38 registration fee and your VW museum certificate. You'll probably be asked to come and show your car for an inspection at your local DVLA office. You should then get an age related number from them (should be 'B' reg for 1964). 🙂