Sorry found this old thread and the question sprung to mind
If you're looking at the ATPL exams, you have six sittings in total and 4 attempts at each paper. So no, you can't do them one at at time.
Ok, then you could do 3, 3, 3, 3, 1, 1 (provided you don't fail any paper) which sounds rather comfortable (especially the 1, 1 bit lol) for those in full time employement.
But aren't you required a mandatory brush up from your FTO ?
Say you are with Bristol, brush up for the 8 exams of module one, but then go and take only 3 ?
Would that be allowed ?
ivor