Good evening,
The main body of the church and the tower are the same age would be my guess. The chimney, although possibly altered, is also original. Many small churches had a fire place in the local Lord of the Manor's box pew. He would want to keep himself and family warm.
The 2 parts at the side and the piece connecting tower to church have been added at a later date. Not necessarily at the same time. Hence the different window styles.
The octagonal spire will have been added later also.
There are quite a few examples online of churches with separate towers. But alas this is not one that is pictured.
John915