Where are you residing now? West Coast options have opened up via the Swedish and British CAA.
"Aviation Exam" has a brilliant in depth database which doesn't require to be online, and explains the theory very well. Using their app on iPad/iPhone is very easy. Bristol as recommended is also very good to take practice exams as it has a timer and gives you your score during the duration of the test. Good indicator of your progress. Also the Oxford ATPL CBT's are a life safer.
I think it's smart to equip both passports for opportunities as we've seen this business fluctuate over the years!