Things have got easier now, all the codes like E etc. have gone and now we have a new system:
04 = Feb 04 - Sep 04
54 = Sep 04 - Feb 05
etc.
So HV52LDX would be from Portsmouth, Hampshire and would have been registered Sep 02 - Feb 03
I think those are the months, I'm not entirely sure.
Cheers,
John
Panda Dynamic AirCon (04 Reg)
Rover 216SLi (K Reg)