I also remember modular maths exams, and I didn't like them - as well as the constant preparation, there was also the fact that you couldn't have as many interesting, problem-solving questions that use information from various topics. By the end paper, ok, but sometimes you want to mix topics up more and even on the earlier papers, use different ways of testing. And that didn't seem to happen as much - they seemed more routine questions somehow.
I also know of a couple of pupils who really shouldn't have passed them, given their lack of understanding, but because they had quite good short term memory, they did manage to scrape through by memorising methods that they had no understanding of, but got them the right answer or at least a mark or two. This isn't great either for their understanding, or for what the exam was meant to test - an employer who thinks that with that grade, they could do certain types of calculations would have been disappointed. The pupils would have been better served with an easier exam that tested them on material that they understood, and had time to learn properly. I don't think the modular exams did much for the overall state of maths ability in teenagers, even though it helped specific children get through the hurdle of passing, and I can understand why that was good for them.
I think we shouldn't specialise so early, and allow more subjects up to age 18, with different levels of maths and English and other chosen subjects, possibly that could be taken at age 17 or 18 (or even 16) and then move on to harder levels if you want, or just keep working towards that basic level if needed. And have a whole lot more differentiation in earlier years, rather than forcing pupils to sit through more difficult work when they don't have the basics. There could be different tracks/curriculum from year 8 or 9 aiming for the basic level to be completed at age 16/17/18. In many countries, you have a list of requirements for a diploma at age 18, that requires a basic level of maths that could be done at age 16. After that you could take harder maths or repeat the basic one, and you can combine it with various other subjects that you choose as long as you eventually meet minimum requirements in certain basics. In some countries there is much less empahsis on what year you are in, and more on whether you have completed and passed the pre-requisite for that course.