As Stan has done you can look up lists and buy available personalised numbers in the UK. They are all original numbers issued by the DVLA (Driver and Vehicle Licensing Agency) but which you can look through and choose one that suits you.
The very early numbers are prized most because they are often short and not broken up by prefix or suffix letters.
Numbers up until the early 1960's would typically be three letters and one, two or three numbers e.g. XJW666 but then as the number of cars increased a suffix was added so it would read XJW666A, XJW666B etc. These also told you the year of registration 1963 being "A", 1964 being "B" etc.
In 1983 the letters of the alphabet were use up and so they became prefixes and the numbers and letters were swapped. So now it would be A666XJW, B666XJW,
Then in 2001 the letters ran out again and so a new format came out in Sept 2001 so that Y666XJW would be March-Aug 2001 but the new format (currently in use) would make it difficult to reproduce "666" together as it is in the following format ...
2 letters 2 numbers 3 letters e.g XX-51-XJW - now the middle two represent the year (Sept 2001).
When a car is scrapped its number is available for purchase and sometimes sold if perceived as having value. This site explains and is a sales site.
https://www.nationalnumbers.co.uk/