What are my options for my english horse?

With a 16.0hh Thouroughbred you can do literally anything, so you got lucky by buying the most versatile horse out there. There are really no overlaps between the western and english disciplines so you are going to have to learn something totally new. The overlap I know of is that reining is basically the western version of dressage. But dressage definitely requires a trainer as it is extremely hard to master. Think about what you want to achieve with your horse and also what english riding opportunities are provided in your area.