May I just add something from the DVLA website...
"It is an offence to alter, rearrange or misrepresent letters or numbers in order to form names or words or in such a way that makes it difficult to read the registration number. Characters must not be moved from one block to the other e.g. AB51 DVL, must not be displayed as AB5 1DVL or AB 51DVL. Vehicles with illegally displayed number plates may FAIL the MoT test. The police can also issue fixed penalty fines for illegally displayed number plates. Offenders are liable to a MAXIMUM FINE of £1,000 and in some cases the mark may be withdrawn."
Also, with the increased use of ANPR "they" are getting very hot on this now, so "Caveat Emptor!"
(to mis-quote admin)