I think that Bristol distance learning is only 6 months as well and they have a very good reputation. A lot of people on residential courses at other schools still pay to use the Bristol website as they have a lot of practice questions that have a high degree of relevance to what you will see in the papers.
Cabair's modular residential course is 5 months also but they have specific start dates (about 4 or 5 a year I think) whereas CATS you can start when you like as it just keeps looping around.
I'm 32 now so I wanted to do it quickly but also get good marks so I decided to go full time and move to live near Cranfield. I guess your personal circumstances would dictate the best choice for you - if you don't need to work and can physically get to an in-house school I personally think you learn more by getting face to face with instructors.
The only other thing I'd say and you probably already know - doing the ATPLs in this timescale is going to demand a lot of time every day - residential would be 9-5 then doing practice questions most nights and usually one day out of the weekend.
Cheers