Put your request (politely!) in writing and post it to him Recorded Delivery. I know that sounds weird, but you need proof that he has received your letter. in your letter, advise him he has seven days to adjust the light appropriately, or you will be forced to take legal action, advising that you are sure this will not be necessary - you want to try and avoid a war of attrition with your neighbour. If that brings no response, have a word with your local Council and ask for advice in proceeding - you might want to consult a solicitor who will give adive for a minimum fee. I know all this sounds drastic, but it's muech eaiser, and more effective, than doorstep slanging matches. Goo luck.