Just checking whether you mean Hopton on Sea, Norfolk or Hopton, which is in Suffolk but very near the Norfolk border? I'll assume you mean the first, but if you mean the other Hopton please ask again.
Hopton itself is a quiet place, with a lovely beach, but that may not be much use to you on a cold or rainy day! It's a nice village to walk around and you can have a meal at the pub (White Hart) or, in good weather, a boat trip. However, people on a day out in winter often choose to visit places nearby: The closest is the popular Potter's Leisure Resort. This is normally a place for a weekend break but they have lots of entertainment, fitness and beauty salons, restaurants and bars etc - you could see what they have to offer for day visitors or take advantage of the best offers by making it an overnight break instead.
Alternatively, with Great Yarmouth only 8 miles away you could have a trip there - there is also a bus service if you don't want to drive.