The amount of training you will require depends on lots of factors Age, Aptitude, Commitment to name but a few.
Generally, 36hours intensive training is fine for a complete novice. However, 40or 50 hours may well be needed for a complete novice who does not take naturally to driving.
If taking a full week off work is impractical it is possible to split your course into smaller sections. For example someone taking a 36 hours course may opt to take their training over three days one week and three days the next week.