When I did my distance learning brush-up, there were people there with FAA and other ATPs, and on the whole they didn't find the subjects much easier than us JAA guys with a fraction of their experience.
As for doing it alongside a "real" job, yes, it's definitely possible - I did it myself. Studying on the train on the way to/from work, in the evenings after work, at the weekends.... took me 12 months, some people take less time, some take more. Don't expect to have any social life for however long it takes, that's the only thing!
FFF
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PS - BillieBob, thanks for the quotes from JAR re. different countries. As I understand it (please correct me if I'm wrong), it used to be that you could add ratings (e.g. IR, type rating) from one JAR country to a license (PPL, CPL, ATPL) from another, but that was about it. But some time towards the end of the last year, they allowed you to do the different aspects of a license in different countries, e.g. mix the ATPL exams from one country with the CPL training from the other. Note the difference between ratings (always allowed to do in a different country), and license (must be done in one country until recently). This is in addition to the concession that you've posted about, which are only "In circumstances agreed by both Authorities". Is that pretty much your understanding too?