Can you protect an idea? No. Copyright doesn't protect ideas, only the form in which they are expressed.
If you want a general indication, here's the basic blocks of intellectual property in England and Wales:
Copyright- If your work qualifies for copyright (I can elaborate more), it is free and automatic as soon as you have created something. It could be a literary, musical, dramatic or artistic work, and lasts until 70 years after the death of the last surviving author. It protects against substantial copying of you work, although there are some exceptions.
Trademarks- They are either UK wide TMs or European TMs. You have to apply to register a TM onto the TM Register, and it costs money. They have to meet certain criteria (I can explain them if you need me to), but if they are registrable, you can stop anyone using your TM in the course of trade on identical or similar goods. If you want an EU TM, it costs more. If you want a TM outside of the EU, you have to apply in each country separately, which is a 'ball-ache'.
Passing Off- Because not everybody can afford to register a TM (or the mark might not be registrable because it's descriptive etc), there's an alternative action called passing off. This is where you have been trading under a name, and have acquired goodwill- like a reputation, a reason that people know who you are and return to you for more business. It's harder to prove than TM infringement because you have to prove you have this goodwill (hence why registering a TM is a good plan), but you can use this action if you miss out on a TM.