It's going to be a long haul, because all teachers must have a university degree and QTS (qualified teacher status).
The conventional route would take you 6 years. (2 years to get some A-levels and a C-grade in Science at GCSE. 3 years to study an academic subject at university. 1 year to do a PGCE course). For primary teaching, there are a few institutions which run a 3-year teacher training degree course, which would cut a year off the total.
Other routes are available, but still need to end up with a university degree, so there aren't any magic shortcuts. (You'll need to decide what your specialist subject areas will be. Most primary teachers have responsibilities beyond the education of their own class. One teacher will be responsible for developing maths within the school. Another will have responsibility for music, or social studies, etc. Those teachers generally have degrees in the relevant subject areas. You'll also have to be confident that you can get to grips with differing theories of developmental psychology, educational philosophies and comparative models of education).
Click 'Start', here, to see what options are open to you:
http://www.tda.gov.uk/Recruit/becomingateacher /waysintoteaching/yourroute.aspx
Chris