Hi jamie.dunn, i've just read your post, and I think the answer to your question will rely upon two things. The first is when Realtrack have the new batch of class 144's in stock, and are therefore ready to take orders. Secondly, is posssibly your place in a queue of orders. But if you did select Royal Mail Special Delivery, when the unit is posted, it should arrive the following working day. Hope that this is of some help.
All the best
Market65