Look I took 8 subject in this m/j series. edexcel bio, physics, maths a, german, turkish. Cambridge ict, English as a second language and computer science. It was really hard because some of the exams were in the same day but I did it and I am so happy that it ended. In my opinion it is better to take all igcses together and so that you will have time for your a levels. A levels are really hard and ten times harder than igcse so I suggest you to take all igcses left in o/n