Oooh I had a creepy experience a few months back.
My mum lives in an old farm house which is above a small caving network up on the Mendips between Bristol/Bath. It's in the middle of nowhere and seems to always be in the clouds. I was visiting with my GF at the time and we popped out to pick some blackberries whilst everyone was out. After about 5 minutes we heard what sounded like someone wailing, a really horrible noise but 99% certain it was made by a human. Ran in the direction of the noise and started shouting out to see if anyone needed help but couldn't find anyone, even searched near the cave entrance but found nothing except for a herd of cows which looked a little confused.
We carried on picking blackberries putting the strange noise down to the cows even though I wasn't convinced. We started walking down a very thin trail which was surrounded by dying bracken and brambles which was about 3-4ft high when my senses went into overdrive (Hairs going up on end now just thinking about it). Anyway, I could just sense that we were being watched or that someone else was nearby, at the same time we both started to get a feint whiff of mothballs/old unwashed human smell which is unmistakable, I'm sure you've all got the same smell from an elderly relative or a homeless person. Again I started calling out, asking if anyone was there, the undergrowth was that thick that somebody could have been untying my shoelaces without me noticing, we found nobody and both being freaked out headed back to the house.
To this day, I still know something wasn't right. My theories are either a homeless man was running about on the Mendips for no good reason. (Doubtful as it's nowhere near anywhere worth setting up get food/shelter. Only other thing it could have been is someone in the cave network, though the cave entrance was locked up and nobody was meant to be there that weekend to use it.