Re: And this ladies and gentlemen...
What about vintage cars pre-dating 1963?
Just corroborating my vague memory of seeing such cars with a Google image search, shows up at least:
LL 000
LL 0000
LLL 000
000 LLL
This apparently simple parsing task suddenly become a whole load more complex because of overlapping formats which no way to guarantee for example that ABC 123 is LLL 000 and isn't LLL 000L missing a character.
Add into the mix another commenters point about the 'cherished' plates like '007' as well as formats like my previous car of 'L0 LLL' and I think the best you could hope for based purely on the parsing of the registration they entered would be some fun passive-aggressive on-screen hints such as: "You appear to have entered a vintage registration number - are you really parking an Austin 7 or did you make a mistake?"
As other commenters have pointed out, RingGo hooks into DVLA and gets you to confirm your vehivle make,model and colour which is far harder to get wrong.
I certainly think that it should be mandatory for all council and private enforcement systems to perform a fuzzy match of the details entered to cope with such mistakes.
Can any of our antipodean friends on here tell us whether an equivalent database exists in Oz?