There are loads of websites but some of us find them a bit ... willywaving 
The thing with vaping is it's an incredibly fast moving industry with new innovations coming out every week more or less. Everybody has their favourite bits of kit and will recommend something different. You probably won't find a site that spells it out because the advice would be obsolete in a matter of weeks.
Boiled down to its very basics, an ecig is just a curly bit of wire (sometimes two or even more) stuck on top of a battery. There will be some sort of wicking material that draws the liquid to the coil. Everything is just variations on that really.
Is your kit the same as the one I linked to? If you're not sure could you post a pic of your kit? If it is the same then those clearomisers won't take replacement coils, you need to replace the whole thing.
The ones I linked to you can replace the coils, or even rebuild them if that's your bag, but many people don't bother as they are so cheap.
The nautilus is a great option but quite low resistance (1.5 ohms). This means it will draw more power from the battery than your CE4s (and also produce lots more vapour) so you might find your batteries don't last very long between charges. If your batteries are the ones in that link they are 650MaH and I wouldn't go below 1.8 ohms on those or you'll be charging all the time.
I would have a look on UK Ecigstore and MyEpack and maybe choose a few different types to see what suits you.