WASALOADIE
Thanks for your advice. Most probably I will carry on with OAA. I see that there are basically no difference either use OAA or BGS for ATPL studies, it is just a matter of personal and study preferences. However, I checked the forum and surprised nobody asked similar question yet. Also, I haven't seen negative reviews on BGS (that somebody is not happy about them or something similar - all cadets say as one that BGS is really good), while I have seen some negative opinions about OAA.
For me, personally, I dislike how OAA organise the ATPL distance learning course (divide 14 subjects into two phases while BGS have 3 modules - BGS approach is more rational in my opinion), BGS have Accelerator Weekend which might be really helpful (there is no such thing in OAA).