Altering from standard in anyway is illegal, however I have found if you stick to standard digits, allbeit mispaced, that can still be read by camera/cops/public in event of an accident, they are ok with the boys in blue ( touch wood).
What really gets you in the s*** is if you use italics, bolts in wrong places etc, as this means the plates could then not be read in the above instances correctly/at first glance.
By the way the dvla site is great, bought 3 myself, no probs at all, no brokers commision, 3rd partys, transfer fees included in price etc. Would recommend them tenfold over others. Mates of mine have had real problems elsewhere....
Hope this helps.
[Edited by 172blue on 24 July 2005 at 10:36pm]