American here currently working on my US Remote Pilot license. The easiest thing to do would be to call the UK FAA which I believe is called the CAA. The CAA also has a place on their website for drones at https://www.caa.co.uk/Consumers/Unmanned-aircraft-and-drones/.
The rules of flying a drone are pretty straight forward but I found that information about how to handle being near an airport (communication, AirTAM's, and understanding flight space), understanding weather conditions, and basic maintenance extremely helpful. If the CAA offers any training or manuals on those topics I highly suggest you read them.
I'm linking the reference material for the faa here. I expect the UK will adopt similar laws to the FAA. The study guide I'm using for my training is the remote pilot test prep guide. I hope this helps you find some answers.
Edit: please don't fly in or around an airports air space. It can get you in a lot of trouble especially if the drone is at fault for damage to another aircraft.
The air spaces are designed in a cone like shape. The closer you get to an airport the lower the ceiling on a given airspace can change. This is the best example I could find online. Some airports have special rules depending on what they do and how big they are on top of the standard rules.
I originally learned this info from the remote pilot test prep guide.
Ok so I passed with a 98% (the one question still bothers me lol) and here is what I used in no particular order
I read the FAA study guide, did some of the 3DR questions, and searched google and youtube for anything I didn't get and watched multiple videos until it clicked. I did this for airspace, airport markings, weather, METAR/TAFS.
Then I cracked open the ASA study guide and used that to reinforce everything I had been studying while also exposing me to more questions and concepts.
I used all 5 practice tests that came with the ASA book and felt they were very helpful to my actual exam with out using the exact same words.
Don't memorize the questions/answers, learn the concepts! They will try and trick you by changing stuff up, it's best to re-read every question. Learn how to decode METAR, learn where to drop 2 "0s" and make sure you know how to read sectional charts.
The test only took me about 30 min to complete, however I started back at the beginning and re-read every question and answer to make sure I was going with the one that makes the most sense.
Plenty of questions seem fairly obvious to any one who has been flying for a while and practices at least a basic level of safety.
Spread your study time out over at least a week or two depending on how well you cram. I spread mine out over about 3 weeks. The practice test I spread out over 4 days, 2 the first, 2 the second, none the 3rd and one the 4th day, the day before my test.
I took a prep course and bought this book. Haven't tested yet so I can't speak to how effective it was, but it is my path.
https://www.amazon.com/gp/product/1619544687/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
I'm currently studying for my 107 and want to add this to the list of things on here.
I didn't see a direct link to the FAA study guide. This is the one I found here. The problem I have with this guide is that some of the links go to the pilot section, instead of the non-pilot cert. Some of the sections contain only references to other guides so it can feel very confusing.
I'm currently reading the Remote Pilot Test Prep Guide. I think this book does a great job of breaking down some of the more complicated aspects of getting the 107 cert. The biggest headaches for me have been properly understanding airport rules, how to define source direction of planes, and reading air charts. The guide does a good job of covering these topics along with example questions. The other portions of the test about weather, maintenance, and acronyms is pretty straight forward.
For those of you who have never done a test like this before it's exactly like getting a standard IT cert like Cisco or Microsoft. The company who does the testing also does some IT related certs. These exams purposely try to trick you by giving similar sounding answers and an over use of acronyms. So make sure to memorize every acronym you can as these test will use them to trick you. If you fail the exam you have to wait 14 days to retake it so test when you're ready as the window to retake it is pretty big.