Advice on keeping tortoise outdoors

[Gmannnsam]

Would anyone be able to give advice on keeping our tortoise outside?
I am in the process of building an outside home for it and would like advice on heating and insulation for the house i am making. I have made two living areas for it, one is 600x600x300 deep and the other 1200x600x300 deep. I have made a hinged lid which I will weather proof with felt and and have weather strip to keep water tight when it's closed. On the larger area I have also punt an acrylic window in the lid to let the sun through. We live in Scotland so climate not great in winter.

There will also be a large out door area for it to explore.

Any help appreciated.