In the UK, copyright is automatic: there is no need to register it. It is the property of the creator as soon as it is created. However, it is not sufficient to be able to prove that you thought of something before someone else, since copyright does not apply to ideas, but to things created from ideas, such as written material or music. In fact, if you have an idea or concept, the best advice is to record it in detail so as to ensure you have, at least, the copyright of the words expressing the idea. One example is a business idea that, on its own, is not capable of being protected whereas a written record of the business plan would be copyright.
An exception to the rule that the creator owns the copyright is when the creator is an employee. If an employee creates material for you in the course of his or her employment then, as the employer, you will normally be the copyright owner.
If employees or contractors create any form of intellectual property, it is sensible to have a clear agreement covering the ownership rights relating to it: in the case of an employee, this would normally be covered in the contract of employment.
If you discover that someone else is using your copyright material without permission, there are various courses of action you can take.
Depending on the nature and extent of the infringement, you may need to obtain a search order and/or injunction to prevent further use of the copyright material. You may also take various other steps in relation to recovering and destroying the relevant items. In less serious cases, a carefully worded letter that spells out the legal position may suffice.