Stamping on siblings

Siblings A B and C own a residential property in individual shares equally. They have agreed that A should purchase the shares of B and C at full value. A valuer has been instructed and A will acquire his siblings' shares at two-thirds of this valuation no discount for part shares being applied in fixing the consideration.
The value of the property is such that the sums paid by A to his siblings will fall within the lowest band of stamp duty land tax for each individual transaction although the combined consideration for the two transactions would breach the next threshold. Can A pay SDLT on the basis of two individual transactions? Would it make any difference if the purchases from B and C took place on different days?
A telephone enquiry made to the SDLT Office in Birmingham elicited the response...