In all the weekly TV guide papers it said that last night's episode was the last in the series but just checked the BBC listings on their TV site and it shows Holby is still scheduled for next week?
I think the 52/52 then 1/52 is done because it can then have a series number designated to it (The series ends in October), like say Dr Who, only in Holby City's case it is more or less on all year round, i believe Casualty does the same thing.