I have processed hundreds of reviews of marking over the years. To find 4 marks in English would be super super super rare. It is not a remark, it is a review of the marking (this changed a few years ago). They do not remark the paper, they review the marking of the paper, i.e has the initial marker applied the mark scheme correctly. As long as the mark scheme has been applied correctly then they can not change the mark, even if the reviewer may have marked slightly differently had they been the initial marker. This subtle difference comes in to play much more with subjects like English.
Maths, it's either right or wrong so a review of marking in maths is essentially the same as a remark. 3 marks is still a lot to find, but not as much as 4 marks in English.
Our rule of thumb is it's worth trying for a review if you're 1 or 2 marks off a grade boundary, maybe 3 at a push. More than 3 marks we'd advise against unless the grade was very surprisingly low for that student and the teacher thinks there may be a fundamental error in the marking such as maybe a page/question was missed by the board or they've added up incorrectly etc.
If either subject was taken with Edexcel (or AQA as well this year), then I'd advise asking for the papers back. Then asking asking a teacher to look at them. Maths is obviously very straight forward to see if there might be a mark or two missed. English not so easy but if it's 4 marks he's needing then if they were missing, they might be more obvious than just one mark. If teachers think it's worth it, then take their advice on which paper to get reviewed.
I'd advise against getting them all reviewed as 1. It's expensive and 2. I have seen more than one instance where a student gained 2 marks in one paper, but lost 2 marks in another paper, so overall their grade didn't change, even though they did get 2 extra marks in one paper
Edexcel is free and instant for school to get the papers back. AQA is also free, though not instant, I haven't had any back yet from AQA so not sure of their timescale.