Can I use photographs of another extension to explain my ideas?
Yes, they can communicate appearance or a particular feature. Explain what appeals to you rather than assuming the whole design transfers to your property. The existing building, requirements and relevant approvals must be assessed independently before a construction proposal is agreed.
Should fitted furniture suppliers be coordinated with the builder?
Where fitted furniture affects dimensions, service positions or construction details, coordinate its supplier with the responsible designer and builder. Identify the current drawings, measurement responsibility and the stage at which the space must be ready. Share revisions with everyone whose work depends on them. Keeping the purchase separate is possible, but its construction interfaces should not be omitted from the main brief.
Can a room be quoted without agreeing its intended use?
An initial discussion is possible, but the use helps define layout and finishing requirements needed for a meaningful construction scope.
How do product lead times affect the building programme?
An item needed for a particular construction stage can affect the sequence if it is not available when required. Agree who orders it, when dimensions are confirmed and how delivery is coordinated. Ask about the consequences of a substitution before accepting one, especially where it changes the design. A programme should reflect these dependencies rather than assume every selected product will be immediately available.