MGJason, these days most UK based integrated ATOs do a three module system it will not make any difference whether this is Airline 'sponsored' or self-funded as they are usually sitting in the same class.
Therefore assuming you pass everything first time you should take about 8 months & 3 sittings then move onto the fun bit.
The order of subjects will depend on that ATO, there is no hard & fast rule as to what comes first but as Met underpins everything it makes good sense that this comes first & you really need to do GNav before Flight Planning.
As you have already started on your ATPLs as others have said you must be mad to consider switching to integrated as your PPL will count for very little. I suspect like lots of others you are struggling for whatever reason with distance learning (DL) therefore you have 4 options:-
1. Give up now - joking!
2. Continue with DL & ask assistance from your ATO.
3. Continue with DL & get some extra private tuition for the subjects you are struggling with - a popular but not cheap option.
4. Stop DL & switch to attend a full-time classroom based ground school, as you haven't sat any exams yet NOW would be the time to change. Of course there is a cost to this, course fees and associated expenses, no income for 8 months and you are unlikely to get any refund from the current ATO.
Whatever you decide, particularly given your situation do not go integrated.
Semi-retired GNav, FP & M&B Instructor.
Please send me PM if required.