Thanks for posting the pics Paul. Your head is perfect, you are one good looking bald guy. How long did it take your barber to shave your head smooth? I agree with using a beanie to keep your head warm in the winter. Try using a mild liniment oil after shaving smooth, the sensation i awesome. Best regards.
15 minutes is quite fast. My barber takes 45min to 1hour to make my head completely smooth, he uses a straight razor.
About Winter time... you'll feel some cold, but that's not caused by your scalp. Extremities (like nose and ears) are more sentitive to cold. So, simply protect your ears and you'll feel warmer.