Hi
Why not go to Univeristy and complete a degree. Whilst at Uni join a UAS or go for a busary. It would stand you miles ahead of a guy with no mil experience.
Other suggestions would be to join the cadets.
Even if you have a degree or A levels you would need to have GCSE English and Maths (maths related subject) at grade C or above for officer entry.
Hope this helps a little