Taking 1.5 hour or 2 hour lessons can aid your progress when learning to drive, allowing more time for learning new skills.  Pupils taking longer lessons tend to do better than those doing 1 hour a week, remember if you practice 1 hour a week that means there are an other 167 hours before your next lesson.

If you can not concentrate for 2 hours in one go then doing two 1 hour lessons a week can be just as useful.  It will not cost any more and in fact can cost less over a course of lessons as you spend less time recapping on previous learning that may have been forgotten  from the week before.