Buying the other party's share in a jointly owned house

[rockin_robin]

My brother and I jointly bought a house several years ago and have a joint mortgage. When he moved out he continued to pay his 50% share on the agreement that when the 2 year deal expired I would buy his share.
We are listed on the land registry as tenants-in-kind

My partner and I now live in the house and have agreed a price of �70,000 to pay my brother for his share which will be funded by the sale of her property (and also pay off her mortgage) and a remortgage in my partner and my names.

What is the easiest way to approach this given that it can't really be completed until my partner's property is sold and also would we be liable to pay stamp duty on the money we give my brother to pay for his share ?

[Nether Edge]

No Stamp Duty Land Tax at �70 000, so that's OK.
You could link the 2 transactions, so completing both on same day. When she sells, her funds can be re-used on your joint purchase.