A BTEC Certificate (30 credits) is the equivalent to 1 As level, the Subsidiary Diploma (60 credits) to 1 A level, the Diploma (90 credits) 1.5 A levels and the Extended Diploma (180 credits) 3 A levels.
for example, the 30 credit qualification requires a student to complete 3 units of work, the Sub Dip 6 units, the Dip 9 units and the Ext Dip 18 units.
If he is doing this with 3 A levels, then he would be undertaking the Sub Diploma (or at a push the Diploma). the specification can be accessed here
To undertake this together with 3 A levels is a lot of work, and I would not recommend this with Applied ICT.
If you look at the specification here then you will see that the 4 out of the 6 units studied upto A2 is through coursework.
Together with a BTEC Diploma that means 15 coursework units for the 2 qualifications which is a lot of work.
The difference between ICT and computing is vast! in ICT you learn how to use software to solve problems (basically how to use software to the fullest and a little bit about networks) whilst in computing you learn about computers from the base upwards (a lot of coding, which needs students to be very logical and it is a 'hard' subject to do)