Anyone know anything about copyright?
Yes I do. 
I’ve recently found out that the editor of the magazine has published a book of compiled articles over the magazine’s history. Some of my articles are in there
As the author of each article (an original literary work), you are the owner of the copyright: s.11, Copyright Designs and Patents Act 1988. The two main exceptions to this are if you are an employee (in which case the employer owns copyright) or if you have signed a contract saying something different.
www.legislation.gov.uk/ukpga/1988/48/section/11
By submitting the articles for publication in the magazine, you have granted the publisher an implied licence to publish in the magazine. Implied terms are construed very narrowly to be only as much as is necessary to give the contract effectiveness. Here, all you need to make the contract effective is to agree to it being published in the magazine.
I would write to the book publisher and say that the publication in the book is outside the terms of an licence agreed. The licence by reasons of business efficacy and custom and practice was only in respect of publication in the magazine. The publication in the book is making a copy of works of which you are the copyright owner.
They therefore owe you a licence fee for the publication. It's unlikely to be very much probably. Depends what the going rate was. To put a value on it, either start with what you were paid for the article at the time and increase it by inflation or start with what your current charging rate would be.
If there is copyright infringement here (which no one can advise you on finally on the internet without seeing all the documents etc), the magazine may also be liable as a joint infringer for authorising the book publisher to make a copy. This assumes the book publisher and the magazine publisher are different companies.
The Remedy will usually be the licence fee you would have charged with possibly an uplift to reflect flagrant conduct on their part in some cases or where the licence fee is not enough compensation. If you went to court you could also ask for an injunction (an order stopping them from doing it again) if you were that bothered about it. If you are writing to them, you can ask for an undertaking they won't publish your copyright work again without a licence. Depend whether you care about that or whether you just want some money now.
All of this comes with a heavy disclaimer that as I said, it's not possible to give reliable legal advice on a public forum without seeing all the documents as things can change massively by tiny alterations to the factual situation.
For example, their standard terms and conditions may contractually oblige you to sign a copyright assignment if they ask for it. That would give them an argument they are the real owners. They may have been publishing books like this for years and argue it was known to all their authors as an implied term. I could go on but you get the idea. Tiny factual changes may make a big difference which is why the best you will get here is very general advice.