Someone please correct me if I am wrong
You can start your 28 hours CPL training on a single engine, doing the first 20 hours on that and the last 8 hours on a twin engine. This means that on the day of your CPL test, you can also do your twin rating test at the same time.
You then go back to a single engine for the beginning of your IR training and switch back to a twin half way through your IR training to do your IR test in a twin engine.
I did it this way for CPL, 18 hours single, 10 hours twin.
I started ATPL correspondence course when I had about 100 hours total. You have to have the ATPL exams finished and 150 hours minimum before starting CPL course.
Your night rating is only needed before IR test I think so you can do that anytime along your training???
On an integrated course, you WONT have a PPL.
Its the cheapest way. Al;though it took me many years doing Modular, I would say I spent about £45,000 in total.