Strictly it is illegal, but I dont think anyone would bother about it - they dont around where I live - there are a variety of mis-spaced number plates here, but seem to be ignored.
This will tell you more - but just please yourself on the spacing!
http://www.regtransfers.co.uk/main/acryliclaw.asphttp://www.regtransfers.co.uk/main/acryliclaw.asp
Brief rules with regard to the display of number plates are as follows:
The Registration Mark must be owned to display the related acrylic number plate on your vehicle.
Lettering should be black on a white plate at the front and a yellow at the rear.
Number plates should be easy to read and conform with the British Standard.
Lettering and spacing must be of a set size.
You must not alter, rearrange or misrepresent the letters or numbers.
Spacing for number plates fitted after 1st September 2001
Spacing for number plates fitted after 1st September 2001
Characters
Height
79mm
Width (except the figure 1 or letter I)
50mm
Stroke
14mm
Space between characters
11mm
Space between groups
33mm
Top, bottom and side margins (min)
11mm
Space between vertical lines
19mm
Mandatory Character Font
All new number plates must contain the new mandatory font.