Alright, this will probably be a little long, but I'm going to try to hit all the bases for you. No links because I'm in the US, so I don't know the UK vendors, but I'll give you names so you can search them out yourself.
Basically, all electronic cigarettes and vapor setups work on the same basic principle - take a liquid with nicotine in it, heat it enough to turn it into vapor (kind of like fog) so that you can inhale it. To do that, we need 2 basic elements.
The Battery
This part supplies power to the heating element, and the nicer ones are usually called mods. How much power is supplied can have a big effect on how much vapor is produced, how hot or cold the vapor is, and how quickly you use up the liquid. There are 2 basic categories of batteries - variable (or regulated), which allows you to adjust the power output to your tastes, and mechanical (or unregulated) which have one power setting. They can range from a basic "cig-a-like" style meant to look and feel like a real cigarette, all the way up to devices that have almost as much electronics as your cell phone, but the thing they all have in common is that they power your heating element. Some of the VERY basic (and not very good) batteries are "automatic," which means they have an air sensor that turns the power on when you suck air through - while it sounds attractive, these don't work very well and are not recommended. The rest of them are "manual," meaning they have a button you push to control the power. While the button is held down, power flows, and it stops when you stop pressing the button. All batteries have a connector on one end that matches up with a connector on the atomizer. The industry has pretty much standardized on a connector called a 510 connection (named after the first electronic cigarette model that used it). Another very common one is an Ego connector, which also has a 510 in it, so it will work with both types, although these seem to be used less and less these days.
Different people like different things, but for most newbies, the ability to change the power level to find what's the most satisfying to you makes switching over from cigarettes (referred to on the boards here as "analogs") easier. If it's very important to you that your new device looks and feels kind of like a cigarette, my recommendation is either an
Ego Twist or a
Vision Spinner. These are pretty much the same thing, just different brands, and you'll want to have 2 or 3 of them on hand so you can put a fresh one on while you're recharging the old one. They're little cylinders with a dial on the end that will change the power level. If you don't care if it looks like a cigarette or not, then my top recommendation is the
Itaste MVP 20W. This guy is an inexpensive little box about the size of a pack of cigarettes with a long-lasting built-in battery, buttons to change the settings, a display so you can see your settings, and a usb port you can use to charge your cell phone in a pinch. It charges by USB and can be used while charging (this feature is called "pass-through") and lasts a couple of days, so you only need one. The
Itaste MVP2 is also a good one, but it doesn't have as large a range as the 20W, so you may end up upgrading sooner. You'll also see a lot of people here recommend the Eleaf Istick, but I strongly prefer the MVP - it has a smooth output, while the Istick alternates rapidly between high and low power to average out to the level you've set it at. That alternating can be a much harsher vape.
The Atomizer
This is the part that does the work. Inside is some way to hold juice (usually a tank of some sort, but some of the more advanced options work in different ways), some sort of wicking material that will transport the juice from the holding area to the heating element, and a heating element that's a wire coil that heats up when power passes through it. The wire is essentially the same stuff that's in a toaster. There are a million different types of atomizers, and new ones come out every day, so I'm going to stick with the type usually recommended for beginners here. You'll certainly learn about the other ones over time, especially if you hang out on the forums. The best thing to start with is a clearomizer (the word is a combination of "clear" and "atomizer"), which is a glass or plastic tank that holds juice with a replaceable cartridge containing the heating element and wick. You typically change your cartridge out every week or two, and they're sold in packs of 5 or 10. Most clearomizers come with 2 cartridges to start with, and you'll want to have some extras on hand. Every once in a while you get a bad one.
As I mentioned before, these tanks are either plastic or glass (pyrex, usually), and plastic is cheaper, but glass is usually the better choice, because juices with certain types of acidic flavors (citrus, cinnamon, that kind of thing) can actually react with the plastic material and eat away at it over time, cracking the plastic and breaking your gear.
Recommendations here: If you want the smaller cigarette form factor, I like the
Kanger Aerotank Mini. If the cigarette size doesn't matter, then the
Kanger Aerotank. They're essentially the same thing, but the larger one holds more liquid (juice) at one time, so you don't have to fill it up as often. You'll also see a lot of people here who like the Aspire Nautilus and Nautilus Mini, but I prefer the Kanger products because of the wicking material. The Aspire stuff uses a ceramic fiber wick (kind of like fiberglass) and I don't know enough about it to feel comfortable with it.
The last thing you'll need is juice. This comes in about a billion different flavors and with different levels of nicotine, and it's totally based on personal preference. Most people say you should start at the 18mg nicotine level if you smoked more than 20 cigarettes a day and 12mg if you're under that, but everyone metabolizes it differently, so that's just a starting point. If you get a headache from vaping, your nicotine is too high, and strong cravings for a cigarette usually mean it's too low. The best recommendation for juice to start with is to find a local vape shop and try a lot of them out. Most stores have a tasting area with samples of all of their juices and a device to test them on. Pick up a few you like and you can usually order more of it cheaper online when it's time to refill. It usually takes people some time and a lot of trying out different juices to find their go-to flavor and brand (if you see the abbreviation ADV on the forums, it stands for All Day Vape, and means "a flavor I can use for long periods of time without getting tired of").
So hopefully that helps. Good luck, welcome to the club, and enjoy your new adventure!
tl;dr: My top beginner recommendation is an Itaste MVP 20W with a Kanger Aerotank, but if it's important to you that it looks and feels closer to a cigarette, go with a few Ego Twists or Vision Spinners with a Kanger Aerotank Mini. For juice, find a shop near you and try a lot of them.
EDIT: In the time it took me to type this out, you got some great recommendations. Looks like I'm a little slow today.
