There are a number of commercial organisations in the UK offering ‘copyright registration’ of original works – for a not-insignificant fee.

This is very different to the registration on offer in the USA, which is a service run by the USA Government’s own Copyright Office. Historically, it was a legal requirement in the USA for work to be registered in order for the originator to benefit from copyright protection. This requirement has been mostly superseded by the Berne Convention however the US still requires registration for works of U.S. origin before the owner can pursue a claim in court, and provides legal advantages to copyrights that have been registered.

There is no requirement for registration in the UK. Your source for all definitive information should be the UK Intellectual Property Office. Check out the succinct information on Automatic Protection and what the UK IPO has to say about Copyright Registers.

Compare these statements made by a commercial service and by the UK IPO on sending a copy to yourself in a sealed envelope:

The commercial organisation says:
”You could post a copy to yourself, (and we are still amazed how often this is quoted as ‘the way to prove copyright’, but the reality is that as the copy you post remains in your possession, you have ample opportunity to tamper with the contents. Even if you did successfully use it, (and it would be a pretty poor lawyer who could not bring some doubt on it as evidence), once you used it, it has been opened and no longer sealed evidence if you need it again in an appeal or future infringement.
(What they don’t say is that if you had to use it in an appeal, it would carry the same evidential weight it did in the original case and that if there was a further copyright dispute on the same image, you could refer to the previous dispute. Evidence of a previous win is likely to cause subsquent disputes to be settled out of court.)

Whereas the UK IPO says:
”Is the registration likely to be better than the evidence you can create for yourself by sending a copy of the work to yourself by Special Delivery post and not opening the envelope upon its return?”

Note that neither registration nor sending a copy of the work to yourself show that you were the creator of the work. Keeping copies of all your drafts and any other material that shows your connection with the particular copyright material as you develop it could, however, be useful evidence if you ever have to prove that you are the author.

Some of the commercial registration service websites look very ‘official’. They are not, they’re commercial organisations and they offer – at a price - a service that is perfectly legal but may be of limited value in the event you need to prove copyright. They (at least, the ones I have seen) don’t offer any practical assistance in the event of a copyright dispute, they simply offer to provide proof of registration which is, don’t forget, not definitive evidence that you are the creator of the work.

There’s probably even scope for an argument that posting your work on dA provides as much evidence as paying for a registration service