Hello,
If you are hiring an architect, please make sure the deliverable is properly stated and timeline. Please make sure if your builder required autocad files your architects allow you to buy on behalf and able to release the autocad file to you.
costs of rebuild is very hard to determine without looking what materials but please open eye big big if they are quoting you M&E like 700K even 500K! I had one quoted 800K in the tender!
You might want to make sure your builder is a responsible person too.