In the UK Teaching Assistants are still not officially required to hold any formal qualifications. However, in reality most schools now only fill new Teaching Assistant posts with qualified people. This means completing a Teaching Assistant Course is a good move.
Finding the correct Teaching Assistant course for you takes a little of your time and some careful research. There are 2 main kinds of Teaching Assistant courses available. They are divided up into work related or work based courses, a subtle but important difference. Which course you can take depends on your personal work circumstances.
The NVQ courses are all work based. To qualify to do an NVQ course you need to currently be working in a classroom, in an assistance role. You will also need to find a teacher or a similar person to act as a mentor for you. Your role at the school need not be a paid role you could just be working at the school as a volunteer.
Instead of taking an NVQ course you could choose to take a BTEC course instead. Like the NVQ a BTEC course is work based, so you must be working in a classroom to complete the course. There are 3 levels of BTEC course, which is right for you depends on your current level of responsibility and how experienced you are. In order to take a BTEC course you usually need to have passed a few GCSEs or equivalent qualifications.
There are several other Teaching Assistant Certification or Diploma courses that do not require you to be currently working in a classroom. These are considered to be work related courses. You can take these courses remotely without stepping foot in a classroom, however at the end of most of these courses you are usually assessed in a classroom environment.