She is the designer who made bunting, table confetti and cake toppers staples of party decorating. Yet you’re unlikely to have heard of Meredithe Stuart-Smith. The US-born entrepreneur began her business at a glitter-strewn kitchen table in 1985. The luxury department store Bergdorf Goodman, in New York, was her first client and she has been quietly busy ever since. Today, Meri Meri stationery, homewares, toys and reusable party trimmings, in her trademark pastels and neons, line the shelves of stores across the world.

“I’ve always designed for parents like me, who want to add a bit of magic to their children’s lives,” says Stuart-Smith, a mother of two. Many of those designs began here in the Cheltenham home she shares with her husband and grown-up son (her daughter now works in Birmingham). The four-bedroom property is set in a stucco-fronted 1840 rectory, which was sliced into three apartments in the 1950s. “The proportions are grand, but it’s not an overly elaborate house,” says Stuart-Smith, who has kept the decor accordingly “modest”. Walls are washed in a concert of bluey-whites; the original, wonky floorboards painted a shiny cocoa brown. Like her designs, the charm of this house lies in the details: a row of Surrealist plates, the swan-shaped cushion afloat on a petite sofa. “I’m drawn to things that are clean-lined, with a bit of fun thrown in,” she enthuses. “I love wallpaper and colour, but I couldn’t live with that intensity. I like to be able to see the wood through the leaves.”

Stuart-Smith and her English husband, who runs a medical equipment business, moved here 20 years ago, lured by good schools, the cheese shop and the curative waters. “I’ve always liked the idea of living in a spa town.” The three-storey property, with its views of the park and creamy sweeps of Regency terraces, needed a great deal of work, which they tackled floor by floor. “The last owner had lived here for 50 years so we had to do everything. Wiring, plumbing, new bathrooms. We did the renovation in stages, moving from room to room like nomads.”

‘I value possessions for their meaning’: the living room with Philippe Starck chairs in Missoni print. Photograph: Beth Evans/The Observer

A few years ago they uprooted the kitchen, from the basement, to the ground floor. “I’d read an article about Jasper Conran’s apartment where he’d put his kitchen in a classical room with a cornice and fireplace. I thought, ‘That’s what I want.’” An interior-designer friend, Pip Isherwood, helped out. The kitchen units are Ikea, the frugality offset by a long stretch of glossy stone worktop. Instead of pendant lights, a hand-blown glass mobile (from Anthropologie) dangles above. Thin, floating shelves are lined with Stuart-Smith’s favourite Fornasetti plates and ceramics by local potter David Garland. “Nothing is precious – just to me.”

I love wallpaper and colour, but I couldn’t live with that intensity. I like to see the wood through the leaves

She added the new double doors that lead to the sitting room. The shutters and fireplace are original, but the hearth is made from aubergine slate, originally used as the surface of a billiards table. The ceiling soars to almost 3m high but, like everything in this household, nothing is too formal or overdone. Gilded mirrors are propped nonchalantly against walls, mismatching rugs scattered across floors.

The dining table, the setting for countless birthday parties, is Habitat; the Philippe Starck chairs, in a loud Missoni print, add requisite fun to the all-white setting. Instead of a “zillion dollar” chandelier, a friend made a pendant light in the hallway from cardboard rolls wrapped in brown paper, for retro effect.

Stuart-Smith, who moved to the UK in 1996, has always travelled light. The few possessions that this low-key creative does have are treasured not for their value but for their meaning. “Almost everything here tells a story,” she says.

‘The proportions are grand, but it’s not an overly elaborate house’: coordinating bedlinen and cushions bring warmth to the bedroom. Photograph: Beth Evans/The Observer

The steamer-trunk coffee table came from her first apartment in San Francisco. “I always think about replacing it with something fabulous, but I can’t seem to do it.” Upstairs, the Victorian sofa belonged to her husband’s family and doubled as a bed on their voyages to and from India. Some of her favourite pieces are the portraits of Native Americans by Leonard Baskin, a US-born academic and artist, who moved his family to Devon to be close to his friend, the poet Ted Hughes. “I’ve been collecting his work for 20 years,” says Stuart-Smith. “It keeps me grounded.”

Art, interiors and fashion have always influenced her designs. It is what sets Meri Meri pieces apart and explains why Victoria Beckham has one of Stuart-Smith’s sparkly reindeer backpacks and Sarah Jessica Parker was spotted assembling a Meri Meri flamingo piñata on Instagram. “Couture” fancy dress – swan capes, tulle skirts – is a recent addition to the range. “Last year I went to the Heavenly Bodies show at the Met and found the perfect idea for our angel wings,” she says. “The Mary Quant exhibition, at the V&A flooded me with ideas for ’70s-inspired patterns. At Meri Meri we’re always ready to play.”

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Interior styling by Sania Pell