Just to clear this up you can run pressed plates only united kingdom font and at a standard size they also have to have the bs number on
My mate runs a set front and rear pressed uk plates with all the correct
bs numbers the police pull him but can do nothing and they HATE it 
The British Standard in
not to do with pressed plates. It covers ALL plates.
Seeing as people are too lazy to read the link.
VEHICLES REGISTERED ON OR AFTER 1ST JANUARY 1973 AND BEFORE 1ST SEPTEMBER 2001 (OPTIONAL SPECIFICATION)1. The plate must be made of reflex-reflecting material which, as regards its construction, colour and other qualities, complies with the requirements of—
(a)the British Standard Specification for reflex-reflecting number plates, published on 11 September 1972 under the number
BS AU 145a(2), or
___________________________________________________________________________________
VEHICLES REGISTERED AND NEW REGISTRATION PLATES FITTED ON OR AFTER 1ST SEPTEMBER 2001 (MANDATORY SPECIFICATION)1. The plate must be made of retroreflecting material which, as regards its construction, colour and other qualities, complies with the requirements of—
(a)the British Standard specification for retroreflecting number plates published on 15 January 1998 under number
BS AU 145d(1), or
_____________________________________________________________________________________
BSAU 145D
The British Standard sets out the physical characteristics on the number plate. This includes:
Visibility
Strength
Reflectivity
The British Standard also requires that a number plate must be marked with the following information: -
The British Standard Number (currently BS AU 145d)
The name, trade mark, or other means of identification of the manufacturer or component supplier. (The company who actually make the number plate.)
The name and postcode of the supplying outlet. (The 'supplying outlet' is taken to mean a company whose business consists wholly or partly of selling number plates.)
A non-reflective border and the Euro-symbol with the national identification letters are optional additions.
There shall be no other markings or material contained on the number plate.
Further information about the British Standards requirements can be obtained at
www.bsi-global.com.
Required:
White front plate (to British Standard BS AU 145d)
Yellow rear plate (to British Standard BS AU 145d)
The registration number of the bearer vehicle in the mandatory font (black ‘Charles Wright 2001’)
Spacing of characters and character groups in accordance with the measurements specified in the regulations. Variation is not permitted
Permitted but not required:
3D variation of the mandatory ‘Charles Wright 2001’ font
Coloured, non-reflective border
National emblem: English St George Cross with “ENG†legend, Scottish St Andrew Cross with “SCO†legend, Welsh Dragon with “WALES†and “CYMRU†legend, British Union Flag with “GB†legend) or Euro Stars symbol with “GB†legend.
No additions or variations are permitted. Common illegal variations are:
Fancy or decorative typefaces
Bolts placed in such a way as to alter the appearance of characters
Adjusted spacing between characters or character groups
Altered characters
Additional logos or symbols, such as sporting emblems and religious symbols.
There are concessions for older and vintage cars. “Historic vehiclesâ€, i.e. those built prior to 1973, are permitted to bear the old-style black plates of either plastic or traditional metal construction.
To quote the DVLA: "Vehicles constructed before 1.1.73 may display traditional style ‘black and white’ plates i.e. white, silver or grey characters on a black plate."
Now, unless someone can point me to where it states that pressed plates are legal, they remain Illegal. just because you haven't been pulled, doesn't make them so.
Jonathan.