Can anyone explain to me once and for all how all the different certificates, points and so on work??

I had hoped to get the hang of it over time, reading Dog World and so on, but I'm forced to admit defeat and ask :)

VHC is the one that stumps me.  It seems to mean 5th

Also what does mid-limit and limit mean?

VHC =  VERY HIGHLY COMMENDED
HC = HIGHLY COMMENDED
C = COMMENDED

Or the cynical version ;-)
VHC - Very Highly Condemned
HC - Highly Condemned
C - Condemned

Mid limit: dogs that have not won 3 CCs or 5 first prizes at champ.shows where CCs were on offer for the breed, in Mid Limit, Limit and Open classes. Limit, same but 7 firsts in Limit and Open.