Christian McArdle wrote:
Of course it also matches the description of subsection 1, a
detached building with a floor area of less than 30m^2.

P.S. There's no "of course" about it. The proposed building is not described
under subsection 1, as subsection 1 defines a building of less than 30m2
that is either far from the boundary or non-combustible. As it is
combustible and within 1m of the boundary, it fails to meet the description
and subsection 1 is not applicable.

There is some confusion about all this. Particularly about the
relationship between planning permission and building regulations. The
crossover seems to vary between councils. Pop along to
http://www.grantham-online.co.uk/planning/need.asp and click on
"Buildings or Enclosures". That suggests you can cover half the
garden in sheds if you want. There is no mention of the 1m rule.

But then if you telephone the planners (not the building inspectors) at
the same council, you get a different answer. AFAIK around here /any/
combustible building, temporary or otherwise, has to be at least a
metre from the boundary. But you don't get that in writing, oh dear me
no.