Once gaining maths and English through the army, can you transfer from infantry to the REME with additional training?

There is scope to transfer however it is not a given. You will have to attend a transferee assessment day where you will have to conduct your GTI and TST tests again which will identify potential available trades. You will also have to sit an interview with representatives from your desired trade. If successful you will then have to go through the trade training pipeline where you will go back to phase 2 training to learn your trade.

Okay that's great thank you. Do you know at what point during training you complete your maths and english? Thanks

Have you started training yet? If you are adamant you wish to serve as REME would gaining the qualifications before you start be an easier route? Initially completing all of your training to then try and transfer will not be a quick process.