In the UK everyone has automatic ownership of any original work. Claiming copyright simply reinforces that ownership and shows the world that you intend to act in the event of anyone copying or using it without your authority.
Of course if it came to that you would have to be able to show that it is your original work, not just lifted from someone else's efforts!
Conversely, if your Defendant can show that the matter complained of was produced independently of your work you would not be protected; there is nothing to prevent people arriving, by their own efforts, at the same result as yourself.
But it is sound practice to stake your own claim on anything you publish.
No formality is required ; you just put the words "Copyright (C)" and preferably the year on the web page and any other media carrying your work.
Claiming Copyright in other countries is a different matter and may need specialist legal advice.
So you need to decide how important it is to you to have protection in those countries and if it is, then I am afraid you are in a different ball game - and not a cheap one!