GCTS
I recently completed the ATPL theory exams with GCTS.
I had a good experience with them and passed all exams 1st time which as a professional pilot is important in money and time as every trip to the brush up and exam center all told came to $1000 a trip.
Steve at GCTS knows his stuff and Phil who is a retired navigator knows more about his subjects than I care to mention.
It's all well and good subscribing to atplonline but when you look at a question and say to yourself "what the hell are they trying to say" and there will be plenty of those, it's good to have someone explain it to you.
Don't think for a minute you can just memorize questions and pass as the examiners are wise to that and make small changes to get you.
You need a combination of understanding, experience and some memorizing to get through and don't get hung up on the fact some questions are well out of date.
I would call Steve at GCTS as he has a huge depth of knowledge of the process and will help steer you in the right direction.
I would finish by saying that it's tough and you have to be disciplined studying and working but it can be done.