I am buying a short lease flat. Do I have to wait the 2 years before I have the right to extend the lease?

Yes. That being said, if your seller qualifies for a lease extension she can start the process for you and on completion transfer the benefit of her claim - you would then have the right to extend your lease immediately. If your conveyancing lawyer is unfamiliar with this procedure feel free to speak to our Lease Extension Team to see if we can help with the preparation of the necessary documentation