It clearly helps to take a few aspirin, read through the legislation, know the criteria they are likely to want met, and conform to it. Its hard work and I can see why there are specialist advisors making a living from it.
Having rung them and asked for the most agreeable procedure, I followed their suggestion of doing a 'pre-prior notification letter' to open a discussion of my plans and be able to clarify any areas of concern, to facilitate a successful application. I detailed a paragraph each on the background of the wood, my management plan, and the need for and description of the building. If I don't say so myself it was well worded, genuine and made a very strong case, and was all bona fide which helps. I think they have a nose for underhand schemes and can smell a rat. I followed this up with a couple of humble phone calls to make contact with the allotted planner for the area and answer his further questions, which I was able to satisfy. His concerns were for example whether having put the building up I would have any intention of then selling the wood. I emphatically said absolutely not, myself and the wood are joined at the hip and I wouldn't sell it for £1 Million, which is true. Its an essential part of a thirty year plan and genuine forestry venture. Presumably once a building is up, other people will eye it as an opportunity for various other uses on the quiet and this bumps up the resale value. I've seen a small wood with a large barn in our region for sale where the speculative price would seem to be to imply it could be morphed into a variety of purposes- not if the planners had any say in the matter.
I still have to submit a prior application, but now I know who's lap it will fall on, I have a reference of the discussion for him to look up again and he's indicated that;
In my opinion, on the basis of the written justification the proposed building would comply with the relevant sections of part 7 of the GPDO relating to forestry operations.
So I think one can assume that if I complete the form carefully with the right plans, its all systems go. I also indicated that further to investigating the costs, fittings and space required for kit the building would be roughly 20 x 40 as a best guess, it might be a few feet either way but wouldn't vary hugely. He expressed relief I said 'feet' as he'd half thought I was talking meters !
Onwards and upwards.