Not a lot, usually I take enough undies and socks for the trip plus a couple spare. The T shirt I wear in the evening gets used the next day to wear on the bike. No jacket (use bike jacket) and a pair of shorts and jeans. Couldn't ride with just heated grips though this time of year, always wear heated gloves. I travel extremely light !
Take gaffer tape, and a few cable ties, and bungee straps used on a few trips on mates bikes from snapped indicator stalks to loose pannier lid etc.