Yeah haha that's a pretty big difference in rankings like.
You're right, M2 does build on M1 and I got everything right on that M1 paper apart from 1 question that I bombed and didn't get very many method marks for. M2 grade boundaries are usually lower as well so I think that makes it easier.
As regards to other maths modules, I can only speak for edexcel but essentially it's a less structured system than it originally looks. Again, this is for edexcel but for maths (AS and A2) you need C1-4 and any two from either s1 and s2, m1 and m2, d1 and d2 or any combination of two from s1,m1 and d1.
For the A star, you only need 180/200 UMS from C3 and C4 and 480UMS overall. It gets more complicated for further as you can swap modules about and stuff but anyway, s1 and m1 are usually done but I hear d1 and d2 are very easy. For edexcel and presumably CCEA you can technically take modules early (I did C4 in January and thankfully got it out of the way so I didn't have to do it only once in june and risk losing my a star and offer) and this should apply to any of the modules (although elimination of January ones makes that more difficult).
There's also a "cashing in" of modules system you might be familiar with in order to get your grade at AS and A2 so if you take modules early, it's useful to check what is module is contributing to what. Again that applies to more further maths when you can use maths modules for further and vice-versa. It's definitely a system you need to know about especially if you're taking modules early or repeating.
I did my school work experience in the electrical and electronic department of Queens which was really good and then last Halloween, I did a week of chemical engineering work experience in Kilroot power plant in Carrickfergus.
There were some Cambridge run engineering like week-long schemes I would have liked to have gone to as well, but I found out about it too late.