I have replied via pm but I’ll repeat the information here for everyone else.
Until DVLA have issued the full CAT C and provisional CE, it would be illegal to take a CE on the road. It’s sensible to allow 4 weeks between passing C and starting CE. Very often the entitlement is in place within a couple of weeks or less. But to rely on this is a folly and will end in tears.
It IS possible, though, to train for the reversing, uncouple, recouple without the licence being in place provided this is taking place on private land and the vehicle operator is in agreement. There could well be insurance implications.
Hope this helps, Pete 