I would agree with GCSE Maths being sufficient (IMO).
I disagree with making sure to do it integrated because modular takes too long. I did everything modular and did my exams via distance learning, when I then did my practical training at what is a primarily integrated school, I found that they were spending longer doing the exams than I had. As what was said, it's all about what you put in to it.
For a reference point, I took 6 months from receiving the study material to having all the exams passed, and this includes a 1 month break over Christmas and a 1 month break after the first set of exams while waiting for results. Other people have done it quicker. Other people take longer.