I did this trip Boxing Day Hadleigh in the morning and Kersey in the afternoon, but it would be even better if you were to attempt this in the Spring, Summer or Autumn.
Plenty of parking in the town so take your pick, travel along the High Street to Bridge Street cross over the Bridge that takes you over the River Brett and just keep taking your next available left turn on foot.
The walk along the Brett is very rewarding especially before the trees are in full leaf as you get good reflections in the river and can see St Mary's Church plus you are among the Spring flowers.
Get to Toppesfield Bridge [Suffolks oldest still used bridge] turn left and immediately left going along the other side of the river near to the weir. Back into the town taking in The Guildhall, Pykenham Gate House, St Mary's Church and all of the High Street. If you still have time Angel Street and George Street beckons with some beautiful old Suffolk colour washed buildings.
Within two miles of Hadleigh is Kersey, everyone can argue on the prettiest village in Suffolk, well this one is definitely mine. It doesn't take long to see everything in the village but St Mary's Church is a must for the view alone.
So in one day you would have seen my favourite Suffolk Town and my favourite Suffolk Village, go for it!