Hi Gemma,
There are two ways you can do it....either a City and Guilds 7303 course over a 10 week period (3.5 hrs per week usually) this is known as the PTTLS or you can dive straight into the Certificate Of Education which is two years part-time or one year full time at Uni...if you already have a degree you would do a PGCE instead of the Cert ed...
I have just finished the PTTLS course which I have loved...it's been a great intro to teaching and makes you realise that there's a lot more to it than just standing up infront of a group of students and showing them what you can do (which is what I thought, lol).
I am starting the Cert Ed in September, you have to have at least 150 paid teaching hours in place before they will accept you on this...so generally having the PTTLS will encourage a college to take you on so that you can get your hours in. A lot of it is chicken and egg...ie..you need students to practice on but you can't get students until you are qualified etc.
Also alot of colleges want you to have your A1 and A2 Assessor Awards before they will employ you...
Another good way to see if it's for you is to ask to shadow a lecturer at your local college...I have done this and it's an invaluable experience.
Good luck,
Sarah x