I did the research too and after screening a few training academies, I found out that finishing course is one thing, passing the exams at CAA is different. The usual situation is that even while having a good weather and by flying 24/7, students can‘t finish training programme earlier because they won’t manage to pass ATPL exams at CAA so quickly. There are a lot of schools in the South which state that their training programmes last 16 months – most of the time they do theory and flying sessions at the same time (spending few hours a day for flying and few hours for studying theory). However, when it's time to take exams, students get stuck passing ATPL exams and can’t go further to study IR.
A few years ago I had a conversation with one flying school from Barcelona, they stated that their ATPL integrated program duration is 16 months. I asked if at least one student managed to finish training during that time interval and the training school answered oppositely as students didn't have enough time to pass exams. So, the duration announced by training schools is a matter of what they consider the actual finish of the course.