Kitchen Extension with Retaining Wall

We have had architect designs to extend our kitchen, where the back wall is a retainer wall for a tiered garden. We would like to move an existing buttress to allow for a better flow of the kitchen, as well as new steel work to allow for the extension... (Budget: £1500 - £3000 GBP, Jobs: Architectural Engineering, AutoCAD, Building Engineering, Civil Engineering, Construction, Interior Design, Structural Engineering)