Mission practitioners came together at the Chinese Church in London, Brook Green, on Tuesday to discuss some of these challenges.
Peter Oyugi, who is originally from Kenya and pastored a church in London for over seven years before joining the Africa Inland Mission, explained that missionaries to the UK often wrestle with the feeling of being a foreigner and experience misunderstandings in communication and in adapting to the culture.
There could also be suspicion towards the foreign missionary, he added. "Even when you get to know them [Britons] the feeling of suspicion just stays."
"One of the biggest difficulties is building meaningful relationships. You can talk and have conversations, but most of the conversations are very superficial. You can't go deep enough," he said.
Joe Kapolyo is originally from Zambia and serves as lead minister at Edmonton Baptist Church, London. He noted that the black-majority churches are continuing to grow, while white-majority churches are declining.
However, he said it remained a problem that although the African church is very strong in the UK and only getting stronger, it is not attracting white people.
"We are not reaching out to the white community in this country, we are not being effective in our outreach to people who have traditionally lived in these islands."
Differing cultures play a part in this, he said, quipping that the British sandwich was a challenge in itself for Africans. He drew laughter when he noted that while food was always a good way of bringing people together, Africans found it hard to get used to "two pieces of bread with a piece of cheese in the middle".
"There are real cultural issues that we sometimes make out to be theological issues," he said.
One solution, Kapolyo suggested, lay in shifting mindsets from "how do we assimilate them to us" to "how do we assimilate to them".
"I have to be prepared to lose some things," he said. "It's harder when you are used to calling the shots all your life and then realise these people on the margins have something I need."
Israel Oluwole Olofinjana is a Nigerian who has been pastoring in a largely white context in Britain since 2004 and is now pastor of Catford Community Church in London.
He said he was shocked to come to the UK and discover that churches established by other Nigerians and Ghanaians were almost entirely full of Nigerians and Ghanaians with very few white British in attendance.
While he said there was a place for mono-cultural churches, it "would defeat the whole purpose of coming if I plant a Nigerian church".
He admitted it was a struggle to adapt to the quieter and far more orderly church style in the UK, joking that he felt like he was "in a cemetery" at the first church he attended here, Crofton Park Baptist Church.
But eventually he got used to the style and went on to establish a successful youth ministry at Crofton Park and become the church's first black pastor, a change he said "empowered" the other black Africans in the congregation.
He admits that pastoring in a white-majority context has meant learning to "think British" and embrace the language and mannerisms.
"I haven't been able to be fully African ... That has been part of my journey," he said.
Regarding black churches reaching out more effectively to the UK's white-majority communities, he said it would be difficult for black-majority churches to suddenly change into something else and that a better way may be to set up multicultural teams who plant a church together. Being multicultural from the outset may help it to grow into a multicultural church, he suggested.
For churches that are already black-majority, he encouraged partnership with local white-majority churches, perhaps around mission projects or joint services.
Samuel Cueva, a Peruvian missiologist, planted a Spanish-speaking church in London in collaboration with St James's Church, Muswell Hill. He agrees that multi-cultural mission is about compromise.
"I will never change the mentality of the British vicar," he said.
He said reactions to foreign missionaries among UK church pastors and congregations ranged from rejection and hesitation, to warm welcome and collaboration.
Cueva said he wanted to hear a stronger word of welcome from key church leaders in the UK and more recognition that missionaries to the UK have been called by God and are part of the body of Christ.
"It would be great to hear more [from UK churches] 'what can I do for you?'," he said.
Although there could be tension in multicultural mission, Cueva was relaxed about it, saying "tension is a part of life and a part of mission and we need to keep going with that tension".
The conference, coordinated by Global Connections, also heard from Alan Black, of London City Mission. With less than half of London's population identifying itself as white British, he said if churches could make multi-cultural mission work in London, this had the potential to positively influence Christianity and mission practice around the world.
"London is one of the greatest mission fields in the world," he said. "For many, the London dream seems to have replaced the American dream."
Black said mission agencies ought to be prioritising Christians who will work in the UK as missionaries.
"There is lots of emphasis on overseas mission but there is a wonderful opportunity to reach people here from all over the world," he said.