A three-course dinner, followed by dancing; Slade’s Merry Christmas Everybody belting out; many drinks consumed; and maybe even a blazing row or a swiftly regretted seasonal snog.

Just an average Christmas party with colleagues? Perhaps not. What makes Friday’s event in the Norfolk town of King’s Lynn unusual is that it will be held in a consecrated church.

Candlelit tables will be placed around the font of the 12th-century St Nicholas’ Chapel, after which guests will move between rows of wooden box pews to the nave, where a disco and bar will run until midnight under the gaze of intricately carved angels in the rafters.

The magnificent chapel has been owned and managed by the Churches Conservation Trust (CCT) since 1992, after being declared redundant three years earlier following decades of declining attendances.

It is one of 347 ecclesiastical properties in the UK – all of which are Grade I or II* listed – now in the hands of the CCT, which aims to both conserve their heritage and find 21st-century uses for these historic buildings. “We are the National Trust for churches,” said the trust’s chief executive, Crispin Truman.

St Nicholas’ Chapel reopened in September after a year-long restoration programme costing £2.7m. Its soaring stone arches and pillars, mullioned windows, flagstones and timbers have been preserved along with a medieval consistory court, where locals were tried for transgressions including witchcraft.

But the church – which still holds occasional religious services – also now hosts local community groups, music concerts and school visits. The ticketed Christmas party is another way for the CCT to open it up to the local community while providing an income stream for upkeep. “We looked for opportunities to diversify,” said Wayne Warner, the CCT’s commercial manager for the south-east region.

A group of 26 NHS staff will form the largest workplace contingent on Friday. Others who have bought £38-a-head tickets are groups from the Kings Lynn Corn Exchange theatre and a local media company. The fee covers a carvery dinner and the DJ; drinks from the bar will be extra. Warner expects to make £1,200-£1,500 profit from the evening, to be invested back into the church.

Beth Greenwood, who will be joining colleagues from the Corn Exchange at the church on Friday evening, said she expected it to be an unusual and atmospheric gathering. “Christmas is about religion, so it’s great to be having a party in a church,” she said.

Locals have been supportive of the party, with some already making inquiries about next Christmas. But the CCT is also sensitive to possible criticism from those who may feel a church is an inappropriate setting for carousing. “Churches should be places of celebration, but we do need to protect the integrity of the brand,” said Warner.

Next year, he plans to offer the church as a venue for conferences, wedding receptions and commercial product launches, as well as building up community and educational involvement.

According to Truman, the CCT is “encouraging increasingly unusual and varied uses of our churches in order to keep these beautiful historic buildings useful and relevant to their local communities and at the same time earning much-needed income for their upkeep.”

The decision to hand over a redundant church building to the CCT is taken by the Church of England commissioners after attempts to sell it have been exhausted. The CCT, an independent charity, gets some public money from the government and the Heritage Lottery Fund, but relies heavily on donations.

“A lot of churches that would have been written off 20 or 30 years ago are now vibrant centres of community life,” said Truman. Some host “champing” – church camping – weekends in the summer; many have become community arts and music centres; a Bristol church is now home to a circus school; a church in Ipswich is due to open in the spring as wellbeing centre run by the mental health charity Mind.

If the public wants these historic buildings preserved, it must accept new uses, says Truman. Once heating, lighting, toilets and kitchens are installed, “these are high quality venues. We’ve got to change the culture because the conservation costs are crippling.”