I'll try and bring a little legal basis back into this thread.
A tent is regarded as a temporary structure, whatever size it is. That's how pubs, country houses and the like manage to put up marquees to run BBQs in for the whole of the summer season. A temporary structure must have a non-permanent base.
Thinking you could use Permitted Development Rights was a non-starter. These apply where you have a structure already in place and want to extend it. You had no existing structure there. And additionally AONB are subject to removal of any Permitted Development Rights under Article 4 of the John Gummer legislation that introduced it. So you'd have had to apply for PP in any event.
Summer houses are permanent structures. "getting in touch with the planners to see if there is a more suitable spot" just won't work - there will be a policy in the Local Plan of the area where you are that says it is not policy to permit development of this type. I'll guarantee it - especially in an AONB. Its not national Government policy to permit development in open countryside unless there is an overriding interest. Such decisions are not taken lightly.
I suppose with the structure there already and a lost retrospective planning application, you've nothing to lose by appealing, but don't hold your breath.
Finally the attached weblink may be of interest. It shows that it is possible to buck the system and run rings around the law - but you have to be dogged, determined and know the basis of the law that underpins the policies. HTH.
http://www.carolinebarry.org.uk/pages/showpage .php?pagename=20050125150753