Hello and welcome, and also good luck in your refurbishment.
When replacing the windows and external doors, you will need odd-leg frames.
These clamp on to the outside of the aperture, rather than sitting inside the aperture as they do in bricks&mortar.
They are not difficult to source or fit - most manufacturers make them, but just make sure whoever replaces them does not just beetle off to the local DIY store and get standard ones off the rack - there is a risk that water will get into the home structure and cause damp.
I would also recommend getting the underneath and chassis inspected as one of the first jobs - it may need some rust removal and coating, and the chassis is the only part of a static that cannot be replaced.
Once that is done - well, have great fun making it into the home of your dreams.Linkback: https://staticforum.co.uk/index.php/topic,690.msg1691.html#msg1691