There are different ways of getting into teaching. You can train to be a teacher while completing a degree in the subject/s you wish to teach. Or if you already have a degree, you can train to be a teacher in one to two years. Whichever route you take, you will combine theoretical learning about teaching with at least 18 weeks practical teaching experience in schools.
The basic qualifications you will need to be able to teach are GCSEs in English and Maths (and a science subject if you want to teach in primary or key stages 2/3) at grade C or above, and a degree at pass or above.
You may be eligible for a grant of up to £2,700 from your local education authority (LEA) and training bursaries of up to £9,000 per year may also be available. Financial assistance for training may also be available from the Royal British Legion. See the link to their website on this page.
A good place to start is the Training Development Agency which has lots of useful information, guidance and further links.