Yes. The annual limits for purchasing Avios are based on the calendar year not your BAEC year, so you could do as you mention and within those couple of days have 48,000 Avios or more...(but you would not be able to buy any more Avios in 2012. You would have to wait until Jan. 1, 2013 to buy further amounts from BAEC.)
HTH.
Last edited by BotB; Dec 3, 2011 at 8:39 am
Reason: to answer the question in more detail