Yesterday, I posted a few links to articles that I thought were pretty good examples of opinion pieces about language. There's always a bit of a caveat with this kind of advice though, because the activity you're engaged in during the exam is basically an exercise to secure marks from the available assessment objectives, rather than actually write something for publication and payment.
That's why you need to be a little bit careful about using anything as an exact style model; while there are really informative and linguistically-informed pieces out there (and I think there's lots of good stuff in the ones I posted), they can also be a little bit thin on language detail and you need to provide that to get your 20 marks from AO2.
What you might want to do - as well as looking at how those opinion pieces work - is have a mosey on over to The Conversation website, where linguists (and psychologists and many other experts) write about their research for non-specialist readers. What you'll be able to see from many of the excellent articles there is how complicated and technical ideas can be explained clearly to people who don't necessarily work in the field.
Some of my favourites also happen to be from some of my favourite linguists...
Rob Drummond on regional accent attitudes
Grammar pedants and fashion victims
Amanda Cole on attitudes to working class and ethnic minority accents
Devyani Sharma on accent attitudes in the workplace