Garden Room Design -- 2

I’m looking for a detailed design for my new 8.4 m × 4.8 m garden room. The roof will sit at a 25° pitch with 300 mm overhangs all around. I want the rafters left exposed on the underside, with rigid foam boards fitted neatly between them so the finished ceiling stays clean and truss-free.
I would like a suspended timber floor, with insulation between the joists, I will dig strip foundations to support this, an additional strip could be inserted at a midpoint for additional support if needed as ground has not been broken yet. (Gravel soil so 450mm foundations already agreed.)
The finished roof will be clad in corrugated metal sheets, so the specification needs to cover correct batten spacing, suitable fixings for that profile, airtight yet ventilated membrane layers, and edge treatments that suit the 25° slope.
Please size the rafters, ridge beam and any perimeter timbers so that local snow and wind loads are fully met; include simple span calculations or reference tables to back up your choices.
(I am in Scotland IV4 to assist with snow & wind loads)
The walls will be timber frame ideally with 100mm PIR insulation between studs, OSB and then timber cladding to the exterior with plasterboard interior.

Deliverables
• Scaled plan, section and detail drawings in PDF and DWG
• Material schedule (timber sizes, rigid foam board thickness, fasteners, membranes)
• Structural notes or calcs that a building inspector can follow