They hold 4 sessions every year and in each session they offer tuition for 4 exams. I have been seeing their entrolment forms since summer 2008 and in past 6 attempts they have not been able to offer tution for all exams. Currently they are having less students for ICAEW. But it might improve by next year.
Tuition is no problem in Middle east several other institutes are also in process of becoming tuition providers the real issue is if you can get a training contract there or not. After just O levels oh no I dont believe its possible. Its even difficult after ACCA/ CIMA or graduation/masters as the mideast market is in crunch. Even if this crunch ends they cant give ICAEW training after O levels or A levels as they also have to accomodate their local population. You should know that already in advisory and Tax departments, knowledge of Arabic language has been made compulsory.
In Canada its the easiest ! They call it Co-op program for CICA but only if you graduate or studying from a Canadian University. You can apply for a Co-op program midway through your 4 year graduation and ur graduation will count for your studies towards CICA and your work in the firm will count for training and the firm will pay your fees. I dont really know full details about it but Canada is a huge country with vast opportunities and very less population. Its also easy in Ireland but Ive heard its difficult to go to Ireland though.
Then Malaysia or Singapore are also feasible options where there are plenty ICAEW vacancies/tuition providers. You can have a good chance in Big4 there but again I am not sure if its possible after O/A levels you must be studying/graduating from a malaysian or singapore university or be an ACCA atleast.