Welsh,
Smiley and the others have hit the nail right on the head. Dress smart casual ( you won't need to go as far as tweeds, Plus fours and brogues) but don't wear trainers, nor hooded sweat-shirt - considers it as a job interview. Even if you get a refusal, you could still offer to help repair fences, clear fallen branches and such like - which might in itself lead to you pointing out how much vermin damage is being done, and then being the best person to sort it out.
Invest in your own future
Good luck
Ogri the trog
Improvise, Adapt & Overcome