For the most part, we are not allowed to accumulate our annual leave entitlement (likely 20 days per year for most of you folks on BMQ). There are exceptions to this rule, but those require certain levels of approval and there are mechanisims in place to actively discourage the accumulation of leave. The long and short of it is that we are all expected to use our full entitlement of annual leave each year. Another thing to keep in mind is that the "leave year" is 1 April to 31 March (i.e. it's the government fiscal year, not the calendar year that we use to calculate this). This means that we all essentially need to use up all of our annual leave before the end of March each year. What inevitably seems to happen as a result of this policy is that many folks often have a few days to use up in March. Often times, this means that a lot of people take leave in March every year (in some cases making March a particularly unproductive month, but that's another issue). Although there is no official policy dictating that block leave will be granted in March, in some units, it could seem this way as everybody scrambles to get it done. It can actually work out well for anyone with kids who wants to take March Break with them.
Because we prorate leave entitlement in the year you that you join, if you've only been in for three weeks at this point, you will only have earned about four days (i.e. two days for each month) annual leave before the end of this Leave Year (31 Mar 14). The school can either give you those four days in a block, or they can allow you to accumulate it. One or the other should happen. I would think it unlikely that they will give you those four days of leave at this point, but I don't know. As others have said, you will receive instructions in due course.
In addition to annual leave, we are also entitled to 11 statutory holidays each year, which includes two days for Easter (Good Friday and Easter Monday). I would be very surprised if you did not get those days off, because both you and your instructors are entitled to them (notwithstanding that we can all be ordered to work on statutory holidays if need be, but we normally compensate folks for that).