I too recently passed BA4. The online questions were straightforward for me but I struggled with the practical, computer updates and reporting parts, in particular producing the financial statements at the end. I still don't know why they didn't come out as I expected.
The number one problem for me was the accounting package I was using (Sage Instant 2014). I had all kinds of problems with installation and finding my way round, and even sum bugs in the system. I spent by far the most time on this, far far more than on studying or other preparation.
The mock exams are a lifesaver. They help to make it clear which statements and reports are required because the sample output provided is from the same package. There were a few reports missing from the mocks output provided, reports that were required on the exam, which was disappointing.
I hope I don't have to use Sage again in the future. I think that there is one more exam to take when I'll need to use it.