You would usually start by joining one of the armed forces. You would complete your basic military training then apply to specialise in bomb disposal.
For example, you could join the army's Royal Logistics Corps as an infantry soldier. After the initial training, you could move on to do further training as an ammunition technician.
In the Royal Air Force, you could apply to become a weapons technician after successfully completing your aircrew or officer initial training. In the Royal Navy, you could train to be a mine warfare specialist, disposing of explosive devices using remote control submarines, or working as a mine clearance diver.
Whichever route you choose, you're likely to need a minimum of GCSEs grades 9 to 4 (A* to C) in English, maths and a science, or equivalent qualifications. You would also have to pass selection and fitness tests to join.