I had to do this with mine earlier this year.

You need to write to Honda UK with your frame number and a cheque for £30 (ish) and they tell you what year it was made.

You then need to get it insured and MOT'd on the frame number, then fill in a V55/5 form from the DVLA and send it off with the following...

MOT
Insurance policy
V55/5
Proof of age
cheque for a years road tax and registration fee (about £60 if I remember correctly).

Hope that helps.