this is the e mail from N.S.A.L.G. he had to give up when he rang, said it was like 'banging my head against a brick wall '

Planning permission for Polytunnels on allotments is not required. You should advise the Council that "the use of land for allotment purposes does not require planning permission because that use falls within the definition of agriculture in the TCPA 1990 - see Crowborough Parish Council v Secretary of State for the Environment & Wealden DC (198043 P & CR 229, DC)'. Section 336 Town and Country Planning Act 1990 states in words of few syllables that 'agriculture' includes 'horticulture'
Section 55 (2) (e) Town and Country Planning Act 1990 states that planning permission ,is not required for .buildings occupied together with land used for agricultural (horticultural) purposes. It follows that planning permission is not required.
This is confirmed by the abstract of page 289 'Local Council Administration' 6th edition 2002 Arnold-Baker and Clayden, published by Butterworth ISBN 0 406 952981.
The use of land for agriculture and the use of buildings occupied together with agricultural land is not to be taken to involve development, for which, therefore, development permission is not necessary. This makes development permission for allotments equally unnecessary.
Structures not covered by this rule’s are permitted development.
[This is footnoted by reference to ss. 55 (2) (e) and 336 Town and Country Planning Act 1990,ancfTown and Country Planning (General Permitted Development) Order 1995 – SI 1995/418].
Part 6 Town & Country Planning (General Permitted Development) Regulations 1995 which talks in terms of planning permission not being required for agriculture (which, it will be recalled, includes
horticulture - section 336 Town and Country Planning Act 1990) buildings. This is again confirmed by the abstract from ‘Local Council Administration'.
Sorry for all of the legal jargon but this should convince the Council that Planning permission is not required. .