Now is a clever time for the Glass House Retreat in Essex to open. In the New Year many of us will look down at our stomachs ruefully, feeling bloated from seasonal overindulgence, and perhaps need a bit more from a trip to a spa than a natter with your mate in the Jacuzzi and a soothing facial. I’d describe the purpose-built detox and wellness retreat in the village of Bulphan as looking at bit like a building you'd find on an industrial estate, although this isn’t entirely fair as there’s also a modernist aspect to it, part severe sharp angles, part clean new build. Which is fitting in that its set its hat at being the only detox, fitness and plant-based diet retreat in the UK.

The project combines the day job of the Jarvis Development Group, a family-run construction firm based in Essex, with the fascination with wellness of founder Joy Jarvis, who based it on her own experience of wellness retreats around the world. Glass House nods to the environment with solar panels, a ground source heat pump and rainwater recycling technology. A good start which continues with the programme of two, three and five-day packages come with a choice of three specialist plant-based diets - Equilibrium, Weight Loss and Pure Juicing. It’s firmly set at weight loss and detox so there’s no alcohol at all and no way to cheat (unless you smuggled Mars Bars in your holdall).

Welcome juices are served in the lounge, which feels like a plush Essex-y five-star hotel, with well-grouped orange and blue velvet sofas, chrome and glass tables and metallic wallpaper shimmering on the walls. I’d taken my sister - a good move as she’s a personal trainer and yoga teacher, so instead of a boxing class, we practice yoga for an hour in the gym. Then we swam in the pool, which, like all spaces here maximises on the views across the surrounding fields, although I’d add a few palm trees to make it feel less stark.

We also sat in the pink-hued salt block sauna, which doesn’t feel that hot but the salt is said to be good for respiratory conditions, boosting immune systems, reducing inflammation and clearing up skin conditions. For a deeper treatment, the retreat offers LifeCube Cryotherapy - a more hi-tech version of the freezing temperature treatment I once experienced in a well-known spa where I was wrapped in bandages and told my blood pressure was so low I was on the verge of a coma.

Then it was lunchtime. The light-filled dining room is a good move, with large communal tables and more velvet chairs in soft foodie shades of cocoa, mustard, and peachy pink to encourage socialising among guests, which is probably useful if you come on your own and don’t like solo dining. Chef Miguel Gouveia devises all of the calorie-controlled plant-based meals and hats off to him. I’m a naturally greedy person who panics if they don’t know when their next meals coming from and I although I eat healthily I don’t fast so I was worried I’d be hungry with just a raw meal. But each dish is so colourful and packed with flavour you eat with your eyes and become full-on combinations such as my choice of vegetable tart with tofu, soya milk and seasonal vegetables or my sister’s vegetable tower with piled-up courgette, peppers and red onion with a basil dressing (others include tacos with guacamole and sushi).

We didn’t stay the night but saw the rooms which are peaceful and comfortable with high, generously-sized beds, Netflix on the televisions (avoid Masterchef and any other food program) and countryside views. So if you want to fully embrace Veganuary, you’ll be in good hands here.

* Two nights from £416pp including one Lifecube session, Dermalux® facial and choice of Back, neck & shoulder or scalp massage, practitioner check-in and check out with state of art body composition analyses and goal evaluation, motivational talks and/or evening activates and daily exercises classes including yoga, pilates and outdoor fitness classes, glasshouseretreat