Type of trade? New dormer & replace slate roof in existing conversion

Ive got an existing loft conversion (2007) in a victorian end of terrace in London NW6. The job is to remove and old & fit a new conservation velux (in a different place), fit a new enlarged dormer (with triple sash), replace the entire slate roof, rebuild the chimney, fit new gutter & downpipes. I also want to lift the existing floor, fit new acoustic mineral wool sound insulation, new chipboard subfloor and a sound proofing board over. Make good plaster and paint throughout the converted loft room. Im not sure which trade to post the job to. Do I want a roofer who does extra stuff, is a loft conversion company going to want a small job like this, or do I want a general builder? Thanks. Mike