I’m being pelted with water. Dangling from a rope. Slipping. Now spinning. “Move your hand, it’s the only way you’ll get down the rock face,” my guide Paul tells me as I try to work out where I go from here. I shoot down and land in a pool. Graceful, this is not.

This abseiling session is just one part of a new wild weekend in the Brecon Beacons with Bristol-based adventure travel company Secret Compass, and its first in the UK.

With 26 years of military service behind him, and months spent volunteering for disaster relief charities, my guide Paul Taylor is stern. “The aim,” he tells me, “is to give you a taste of the extreme expedition lifestyle.”

In reality, though, this is more energetic adventure than true survival mission. Seasoned campers and hikers will have a laugh romping through the countryside while trying out new activities, but those more accustomed to holidaying on a beach and sipping margaritas will definitely find elements testing.

I’d mentally prepped for freezing temperatures, endless rain and sodden, blistered feet, but we’re blessed with glorious sunshine. Our group has 25 miles of terrain to cover, on a trail that varies in intensity from flat stretches to harder, almost crawling climbs. I inflate, and paddle a packraft three miles along a canal; stroll alongside the Talybont reservoir and trudge uphill with an entourage of intrigued sheep. It’s followed by a hike along Craig y Fan Ddu, one of the most spectacular ridge walks in the UK.

The first expletives are uttered on the afternoon of day one, on a painful 500-metre clamber through the freezing-cold water and mud of the Torpantau Tunnel, on a disused rail route. There’s a sense of relief as we make our way to our camp for the night – but there’s one more challenge to get through first. Attached to two towering trees is a stretch of cable, and the only way to cross the river 20 metres below is by ziplining over it. For me – unfazed by heights and permanently hungry – it’s a fast-track route to dinner, but for the acrophobics among us there are anxious, furrowed brows.

With a bit of faffing we make it across, and head into the forest to pitch our tents, finally finishing in gloomy night shadows. Continuing the expedition taster theme, we light the stove and choose between just-add-water pouches of curry, carbonara and fish pie, and dine under the romantic glare of our head torches. The combination of adrenaline and hiking means sleeping is easy, and we drift off to a soundtrack of owls.

The following morning, after cook-in-the-bag porridge, we set off for the big climb. Various routes lead to the top of 886-metre Pen y Fan, and in true expedition style, Paul leads us along the toughest. Near-vertical looking paths wind between steel-grey rocks and pools of icy water lined with snow.

While the group’s pressing on at a decent pace – this is Paul’s 205th summit, and he often runs up here with his border terrier Hercules – the climb is not an easy one. There’s a reason the SAS use the Brecon Beacons as a training ground, and following a leg-wobbling peer over the edge of the mountain, we experience the Beacons’ vicious wind and volatile microclimate on our bum-shuffle on the way down.

The best is yet to come. We gather in a web of ropes and branches as we are talked through our vertical descent. We can’t see over the rock edge, but the woosh of water suggests this will be our trickiest challenge yet. One by one I watch the group – harnessed, roped and a little wide-eyed – reverse off the top of a 40-metre waterfall, before I – legs trembling a lot more than I’d anticipated – grip my rope and step backwards.

I’d expected two days of mentally and physically demanding challenges. What I hadn’t banked on was a hell of a lot of energetic fun to go with it. The softie survivor in me is well and truly satisfied.

• The trip was provided by Secret Compass, whose two-day Adventure Academy weekend costs £250; next dates are 13-15 April, 22-24 June and 14-16 September