I'm keen to adopt a tortoise, I've been reading as many posts as I can.

What are the basics I would need for an outdoor enclosure and what size would it be? 

I don't have a shed or green house, but have seen on pictures, people have used dog kennel type things and cold frames? 

Should it be situated in the sunniest part of the garden?

Thanks in advance x

You will need a hardy species. Also you will need to consider the period between hibernation & temps warm enough for living outside. I'm assuming it will be adult or sub-adult.

A 30cm high wooden sided enclosure is ideal. It needs to be at LEAST 15sqm. 

As you state a house is needed & this needs to be much bigger than the tortoise, so that in poor weather it can move around. The wooden base can be covered with straw. A roof made of polycarbonate [or "Plexiglass"] will aid early morning & general warming. 

This works better than a kennel & cold-frame combination.

This is something you would need to design & build, or have someone build.

Yes the enclosure should be in the sunniest part of the garden with the house entrance facing S.E.. Provide shade areas in the hottest months.

Tom

I would be interested in a Germans or horsefield.

You can get a walk in poly tunnel at a very good price.

Tom