You have it pretty much right. There is 4 weeks of residential ground school even if you do the distance learning.
Actually just 2 weeks of residential ground school - 1 week per module - certainly at GTS in Bournemouth and almost certainly at all the others.
Incidentally, I used GTS and would highly recommend them for the groundschool - they really know their stuff.
The groundschool is reputed to be boring and irrelevant, but apart from a few notable exceptions (eg airlaw history and selcall) it was mostly pretty interesting. Some of the stuff you have to memorize is totally useless. Other bits, such as met, is fascinating and very useful indeed.