Probably the most controlled way young people get their hands on them here, perhaps also the most common (competition/clay/game shooting clubs being the other possibility).
Cadets use a modified (no magazine, one in the chamber) .22 Lee Enfield for short range target shooting on-site (perhaps not all sites have them) and L98 (A1 was magazine fed but manually cocked, the semi-automatic A2 came in about ten years ago while I was going through) rifles of the SA80 family that's standard issue (L85) in the British Army. They also have, but use more rarely, L86 LSWs, and others not issued but may be encountered at 'summer camps' and the like, with training from regulars/TA.
It is a slightly scary thought looking back on it being older now, I'm not sure I'd fancy being an instructor: imagine being a teacher with a 'difficult' child, except you're instructing them in handling a firearm...
I enjoyed it a lot though, and would recommend it for sure.