I don't want to sound rude or unhelpful, but if you have great difficulties in simple mental Maths, do you think you are suited to be a primary teacher? You have precious little time to brush up on subject knowledge once you are on the course, and pretty soon you will be giving lessons, doing mental Maths and teaching children how to solve problems. You may even have to teach top-set Year 6 class. Numeracy and literacy are subjects you will be teaching every day, and lack of subject knowledge and expertise will hold you back. You had a year since last interview to do something about it. For your interview tests, you have no choice but to keep testing yourself using revision notes (KS2 material is good) and online QTS revision tests on TDA site. Read 'how to pass numeracy test' book to give you basic understanding of maths concepts and operations.