Quoting: Andy
What does the one on the Panda mean? (just curious)
DIG 6859
The 68 & 59 are birthdays and the rest is just easy to remember, plus it only cost £50*
* +£80 transfer fee.
As PhilO pointed out Speedy Reg is your friend :
http://www.speedyreg.co.uk/The trick is buy one when the registrations are first released being dirt cheap, every 6 months or so the DVLA release a new batch such as BIG, DIG, FIG, MBZ etc