Anything that you choose to do in life needs to be legal in every single way, shape or form. A big part of the reason why that is the case has to do with the fact that the laws that have been put in place to govern society exist for your protection as well as for the protection of our wider society at any given point in time, and that means that you should do anything and everything within your power to ensure that you are always abiding by them for the most part.
This applies to any UK personalised number plates that you might be thinking of using as well. Suffice it to say that there is no law in the UK that prevents you from using custom number plates, but there are still a few things that you should keep in mind in order to make it certain that you are not breaking any other laws that are currently out there. One example of a restriction in your choice of a custom number plate is that all of the numbers should be clearly visible.
While custom number plates are completely and utterly legal as far as the UK is concerned, there are certain limits that you need to adhere to. These limits will allow police officers to know if the holder of a custom plate has committed a traffic violation, so try to use a number plate that has all of the numbers easy to read and perfectly clear from a visual standpoint. Doing so can help you to avoid any run ins with the law which you would definitely not want to experience at all.