Number plates must comply with the relevant British Standard (BS AU 145d). In order to do so:
1. The numbers and letters must be in the approved font. (You can't have italic letters, curly letters or anything else. There is one, and only one acceptable font).
2. The letters and numbers must comply with precise regulations regarding their dimensions and the spaces between them.
3. The plate must show the name and postcode of the supplier, together with the British Standard mark (who should be properly registered with the relevant authority), together with similar information about the company supplying the component parts of the number plate (if different)..
4. The plate
may display the EU flag (together with the letters 'GB'), as long as it's in exactly the correct format, as defined by the European Council.
5. The plate must
not display any other letters or symbols (including national flags or manufacturers' logos)
http://www.dvla.gov.uk/media/pdf/leaflets/v796 .pdf
Chris