TRS one place, PPR another

Anyone know if it would it be possible to do the following from a revenue point of view.

• Buy a site to build a house on in the future (5 years time approx).
• Use my first time buyer tax credit (1600) to claim relief at sources on the mortgage I take out for the site.
• In the interim buy another site and build a house on it using this house as my primarily principle residence.

Also being a first time buyer will I be liable for stamp duty on the first site I buy.
Thanks in advance

You can only claim owner occupier mortgage interest relief on a mortgages/loans used to purchase your PPR. If you don't live in the property then you cannot claim this relief on any loans used to fund it's building/purchase/renovation.