Mike wrote:
I'm planning on building a new large shed, hopefully with low heating
requirements and a steady temperature all year round to enable me to
use it for woodworking projects.

The shed will be around 0.5m from a shared boundary fence and at least
5m from any existing structures. Will a mainly timber frame structure
covered in fibre cement weatherboarding (with a green roof of sedums)
meet class 0 standards or will I need plasterboard on all the inner
surfaces?

When you say 'large', anything with a floor area more than 15m^2 that
close to the boundary will require a Building Regulations application.
Also check about Planning. If it were more than 1m from a boundary, it
could be up to 30m^2 and still be exempt from Building Regulations.

Building Control will be concerned about structure, external fire
spread, resistance to moisture, and ventilation (amongst other things).

Roofs within 6m of a boundary must be class AA rating, ie,
non-combustible. Vegetation can dry up and represent a risk of fire
spread. External walls must be of 30 minutes fire resistance within 1m
of the boundary, which means in your case that you will need
plasterboard on the inside, as well as the non-combustible cladding.

The thermal insulation requirements do not apply to a free-standing
building of less than 50m^2.

A timber framed building should have a vapour barrier on the warm side
of the insulation. The plywood or other sheathing should be on the
outside of the studs, with breather membrane to the outside of that, and
a ventilated and drained cavity inside of the cladding.
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