One option I was considering was getting an Alpkit Skyehigh 900 + Hunka XL + Thermarest NeoAir Xtreme + Alpkit Masson sleeping bag liner, would this work?

OEX Leviathan EV 900 Review — The Great British Adventure Club OEX Leviathan EV 900 Review — The Great British Adventure Club

A major element of this kit is a good warm sleeping bag suitable for colder conditions - many summer sleeping bags are lighter and contain less fill, which means that if the temperature drops standard summer family options may not cut it to keep you safe and warm. Rab have also added a shiny TILT lining to the interior of the bag, which adds next to no weight but is designed to reflect radiated heat back to the body, further boosting its overall warmth. In this guide, we start with some serious warm winter-ready bags, before moving on to versatile 4-season options, some great bags for bivying and finish with some excellent car camping bags. The bag’s baffles are sewn with variated-width stitching that keeps the down evenly distributed within the bag, preventing cold spots.I’ve had the OEX Leviathan EV 900 for a few years now, and I’ve slept in it at varying temperatures in different climates. As he got older, the hills got bigger, and his passion for spending quality time in the great outdoors only grew - falling in love with wild camping, long-distance hiking, bikepacking and fastpacking. As such, it’s highly moisture resistant, making it a viable prospect even for cold weather use in predominantly wet climates. Both men’s and women’s bags will be comfortable for people who tend to flip from stomach- or back-sleeping to side-sleeping during the night.

Oex Leviathan EV 900 Sleeping Bag | GO Outdoors Oex Leviathan EV 900 Sleeping Bag | GO Outdoors

I’d only be confident stretching this bag down to -9°C (15°F) if I had some extra thick base layers and a warm fleece to wear inside it.Four-season sleeping bags don’t have to cost a fortune, as this excellent offering from Mountain Warehouse proves. When it comes to down, pay attention to the “ fill power”, which is a reasonable indicator of down quality. For safety reasons, you should steer well away from these, and if you plan on camping at -20°C (-4°F) , it’s important you get a bag with a comfort rating down to that temperature. In fact, when we slept in it in -13 degrees C, we had on baselayers, a jumper, a down jacket, thick socks, a hat and gloves.

OEX Leviathan EV 900 Down Sleeping Bag | Blacks

Moreover, the bag packs down small, especially if stuffed into a dry sack, comes with a handy internal stash pocket, and the plush inner liner is soft on your skin. A top-quality 4-season sleeping bag, the Andes Infinium 800 is well equipped to deal with temperatures that drop way below freezing.The fill is treated with a hydrophobic finish, while the shell fabric is made from Gore-Tex Infinium. If you’re after maximum performance from your sleeping bag and you need it to perform in the most challenging of circumstances, this offering from Patagonia, although expensive, will do all you need it to do. When it’s cold, I can hunker down into the bag a little more, tighten up the baffles and zip everything up full. First of all, let’s look at the warmth: OEX claim that this bag can keep you comfortable down to minus 9 degrees Celsius when wearing nothing but baselayers. The bag comes with both a storage sack and a stuff sack in short, regular and long lengths and in both men’s and women’s silhouettes.