I 've had this discussion with the village bobby in the past looking for guidance and I'm still no better off...My question sparked a lively debate between the two PC's in the village station at the time, and this alone opennd my eyes as to how gray the area was!
As already suggested, part of this will come down to the Officers concerned but another big part is the Chief Constables policy...if he happens to have a bee in his bonnet about knives, the message will go down to the rank and file Police that no leeway should be given...
As the law stands, you would need a good reason/reasonable excuse to be in possession of any fixed blade, any locked blade or a conventional folder with a blade of 3" or over if your are in a public place.
So if you are stopped while out stalking you would be fine...
However, if you keep a knife in your vehicle "as a matter of course", you are liable to be done for that as many Police Officers don't consider that "reasonable"...How being a member of a "Deer RTA Scheme" would effect you, I don't know...Again, if the Police wanted, they could simply charge you and let the Courts decide if you were breaking the law or not!
Of course the final judgment will be down to the Courts, but even if your are cleared at that stage, you've still gone through a lot of hassle and I suppose there is possibility that includes having your FAC pulled while its being sorted...