I hadn't realised you were so young

What do your parents think of it ? what kind of hobbies do they have ?
At your age (and mind I'm female) I camped a lot with my friends. It's easier for girls if they go in small groups of two, three or fours.
North Lanarkshire's a big bit of land, are you close to any of the farms ? Find the local Young Farmers group and phone the organiser and explain your age and your interests, and ask if they know of someone local who shoots pigeons or rats on the farms and if he might be happy to teach you a little about it ?
Contact the local countryside ranger service, they will advertise events and the like on line, and ask if they have a local 'friends of' group. These folks get along to do everything from digging ditches to coppicing willow, planting trees to helping to create habitats for everything from insects to badgers.
If you are actively involved with other folks, organisations or the like, it's easier to have a reply to folks pestering you I found.
"Going for a walk. " is always the easiest one I reckon
When we have other localish meet ups, see if your parents will come along with you, even just for an hour or so, that way they meet folks and everyone relaxes about someone young turning up on his own another time.
cheers,
Toddy