Stamp Duty on Inherited property when buying out shares

[saxbyt]

I am one of thre brothers who have inherited equal shares in our late mother's house. I have agreed to buy my brothers out at an equivalent market value of £280k.
There is a mortgage on the house of £62k and threfore our shares are worth approximately £73k each.
I will pay both my brothers these amounts totalling a transaction of £146k. My question is am I liable for stamp duty at all as that is below the £175k threshold? However, if include the value of the mortgage, then I am in the lower band, if I include my own share I am in the >£250k band. Can someone please clarify how this works for me and others? Many thanks.

[maths]

As you indicate, the net equity in the house is circa £218K ie £73K each.

For SDLT the charge is levied on the chargeable consideration which would thus be £149K. However, if you also effectively take over their respective mortgage liabilities (ie £40K) then the aggregate consideration is £189K; SDLT would be chargeable on this amount.

No doubt other contributors better versed in SDLT matters than me will comment on the above.