Hi
My take is this:
APT Renovation no idea
Davide Di Martino no idea
Estbury excellent but tend to do bigger projects, this sounds too small
Nightingale Design and build: heard good things
Battersea Builders: no idea
Lifestyle design and built: no idea
Simbiosi Architects", "studio rose': no idea
Clara Bee: heard good things
Boyarsky Murphy Architects": no idea
Should i get the architect and builders separately? Do I need an interior designer?
It depends on budget. I would get a designer to quote and show you what they can do and do the same for the builder and see if you think the margin is worth it